There are hooks in OoT that were there for Ura Zelda that Master Quest does not address. No, this is not speculation from the media.
Master Quest is not what Ura Zelda was going to be.
The consistant explanation from Miyamoto and Aonuma over the years on Ura Zelda was that it was a second quest with rearranged dungeons. Even if unused content was found, the Ura Zelda project was focused on rearranged dungeons as a second quest, which is what we got with Master Quest.
1999 -
http://www.zeldadungeon.net/Interviews-1999-08-27-IGN-64-Shigeru-Miyamoto.php
IGN64: We played Gaiden a short while ago and it’s very impressive. But we’re curious, will Link grow up in Gaiden?
Miyamoto: I actually don’t know, but I heard that the adult Link will probably appear this time too. Also, if you say that Gaiden on the show floor is really good stuff I can feel very comfortable because that means my staff members have already become better than me when it comes to game creation.
IGN64: Tell us about “Ura Zelda.”
Miyamoto: Ura Zelda is based on The Ocarina of Time for 64DD. It has the same construction of gameplay. It’s very much a parody game based on Ocarina of time, but with new dungeons to explore. It even features the same storyline.
Miyamoto Shows off Zelda 64 - May 1998
http://www.ign.com/articles/1998/05/27/miyamoto-shows-off-zelda-64
Q: Will there be a 64DD Zelda or an add-on?
Miyamoto: I don’t know if “add-on” is the right terminology. For the 64DD, we are working on a Zelda game, which we call “Ura Zelda,” where you first play the initial disk version of Zelda – after finishing everything, you can enter into the world, into the basic design of the same. This sort of WaZelda is now in the works for the 64DD.
Talkin' Zelda with Mr. Miyamoto - Space World '99 - Nintendo.com 1999
http://www.angelfire.com/games5/makzelda/interviews/zgmiyamotosw99.html
Q: After hearing rumors of Ura Zelda for Nintendo 64 Disk Drive, Zelda Gaiden for the Nintendo 64 cartridge format was a pleasant surprise. Can you tell me how these two games came to be developed?
A: We are working on two follow-ups to The Legend of Zelda: Ocarina of Time. "Ura Zelda" uses the same system as Ocarina of Time but uses the 64DD to add game data. The story in "Ura Zelda" will be similar to Ocarina of Time but with new maps and scenarios. Zelda Gaiden, on the other hand, is a completely different game, although it too uses essentially the same game system as Ocarina of Time. Everyone has enjoyed the Zelda series but there's typically at least a 3 year wait between sequels! People who are in Junior High School when they play one Zelda game would be in High School by time the next game comes out, and those in High School will graduate before the next game came out! So, we wanted to make a new game in the series sooner. "Ura Zelda" will use the existing Ocarina of Time cartridge but with different dungeons, and new locations for the treasures. Since the 64DD media is cheaper than a new cartridge, this is an inexpensive way to make a sequel. We may also consider using network technology for "Ura Zelda." Right now, most of the staff is concentrating on Zelda Gaiden.
http://www.zeldadungeon.net/Interviews-1999-08-27-IGN-64-Shigeru-Miyamoto.php
http://www.ign.com/articles/1998/11/18/zelda-dd-the-other-adventure
http://www.ign.com/articles/2000/08/26/ura-zelda-complete
http://www.ign.com/articles/1999/08/21/gaiden-and-ura-zelda-split
Incite Video Games magazine December 1999
http://www.zeldadungeon.net/wiki/Interview:Incite_December_1999
Incite Game Magazine: Is this game system exactly the same or have you added any new features?
Miyamoto: Yes, its basically the same except for the masks. When you wear the masks you can transform into another creature and then you have controls to master.
Incite Game Magazine: Are there still plans to release a 64DD Zelda ?
Miyamoto: Distinct from this new version, we do have another 64DD Zelda game. We’ve currently suspended development because we’re busy with so many projects and we wanted to concentrate on Zelda Gaiden, but we’re still working on it. We weren’t sure which one to do first but for the moment we’ve put the 64DD to one side to do this new Zelda. However, there’s no relationship between them at all. Zelda Gaiden is an original story, while the 64DD uses Ocarina of Time as the base theme. In the 64DD version, certain elements in the story send you off on different paths.
Incite Game Magazine: What’s different about the 64DD version?
Miyamoto: Well, simply put, every time you go into a dungeon, the tasks will be different. If there was a treasure chest in a certain location the last time you went in, then the next time you in it won’t be there.
Incite Game Magazine: Will we be about to play an online Zelda?
Miyamoto: Up to now we haven’t really started to think about this. However, were not looking to create a multi-player on-line system for Zelda. With the 64DD’s read/write capability, we’re thinking along the lines of a new dungeon data downloads, and swapping your data with other players.
Miyamoto and Aonuma on Zelda - Dec 2002
http://www.ign.com/articles/2002/12/04/miyamoto-and-aonuma-on-zelda?page=5
Q: Regarding Ura Zelda, is there any different between the 64DD version that was in development and the GameCube version? Did it use any functionality with the 64DD? And, is it coming to the U.S.?
Miyamoto-san: Although we did develop Ura for the 64DD, it didn’t use many of the special features. So it was very easy to port over to the GameCube without cutting any features. Why we did it, well that was because the 64DD was only released in Japan and it was only sold to subscribers of the RandNet system. For a long time we wanted to make it available for play and find a way to do that. It was expensive to make cartridges, so we had through about different ways. One thing we thought about was tie-ups with magazines. Once GameCube moved to disc media, though, it became much more feasible to make it available. In terms of how we’ve done it, we didn’t want to make it limited edition. So we’ve tried to make it available to as many people as possible.
Also, I’m not sure if you’re aware but Ura Zelda isn’t very different from the Ocarina of Time; it’s more of a second quest. People who played through Ocarina of Time would be able to play through Ura Zelda and get a few laughs at some things, find some things more difficult, and take a few varied paths. However, even if you do play all the way through the end it will not unlock anything special.
Iwata Asks - Zelda: Spirit Tracks - 2009
http://iwataasks.nintendo.com/interviews/#/ds/zelda/0/0
Aonuma: No, we didn’t just start making The Legend of Zelda: Majora’s Mask, not right away. There was actually a flip-side, and in the beginning, the idea was to make a “Ura (Flip-Side) Zelda”.
Iwata: That “Ura Zelda” (The Legend of Zelda: Ocarina of Time: Master Quest) was developed for the 64DD. Ultimately, we recorded it on a limited edition disc that went to people who reserved The Legend of Zelda: The Wind Waker.
Aonuma: Ultimately, other staff members handled The Legend of Zelda: Ocarina of Time: Master Quest. Still, as someone who has been in charge of the dungeons, I just couldn’t get that excited over making a flip-side for them. I couldn’t see it turning into a new The Legend of Zelda, either. But we’d been told to make The Legend of Zelda. It isn’t as though we could just say, “I don’t want to”, and end it there. At that point, Miyamoto-san gave us a tradeoff: he said, if we could make a new The Legend of Zelda game in one year, then it wouldn’t have to be a “flip-side”.
Iwata: Well! So you’re saying The Legend of Zelda: Majora’s Mask was the result of your team picking up the gauntlet he’d thrown down? (laughs)
Aonuma: Yes. That was the deal. But The Legend of Zelda: Ocarina of Time did take three years to make, you know!?
Nintendo Power makes reference to the The Legend of Zelda's Second Quest Japanese name "Ura Zelda" with the headline "Another World".
