Exploration isn't an afterthought. They just said that they'll figure out where the story takes them and then they'll flesh out the explorable world/doable content surrounding the story. That's not an afterthought, that's just having a certain order to things. They are putting in a lot of effort giving players ways to explore the world (car, flying car, trains, luxurious yacts, chocobos, boats in the canals of Accordo etc.) and to provide all kinds of nooks & crannies with stuff to find, optional dungeons to find, more special monsters to hunt, lakes to fish in etc.
They just want the game to have more structure, but that doesn't mean exploration is an afterthought, considering how massive these areas like Duscae seem to be (Duscae seems like it might be far bigger than a single region in XBX). The game's world simply won't/might not be 100% explorable from the start like some Bethesda RPG or GTA technically is. So while it might turn you around if you try to exit Duscae before doing some mandatory story mission(s), Duscae itself seems to be a pretty massive area that holds a lot of exploration within its borders while you work on advancing the story after getting to the region.
And I don't think it differs all that much from Xenoblade X. While it's technically maybe possible to go almost anywhere in Xenoblade X, the reality is the game is structured & designed in a way that you go through different places in a somewhat controlled manner (at first) and are discouraged from advancing too far into the game's different regions before the game wants you to go there & you are ready (level wise, having/not having a Skell). You start the game by exploring NLA's surroundings in Primordia. Then a mission takes you just a little bit further away, deeper into Primordia. Then after exploring the few places of Primordia you can as a low-level loser, you have your first mission in Noctilum but that's largely closed off from you due to super strong enemies that are put near narrow pathways that act as kind of "gates" to the next area. With some luck you can get through but then the next area will have even stronger enemies and such high level nodes that you can't invade ground there to set up checkpoints no matter how hard you try. So you'll explore a little bit of Noctilum and a bit more of Primordia until a mission takes you to Oblivia. After that you basically have to explore all you can from those three regions until you get a Skell 40-50+ hours in and then that opens up a bit more of these regions. And only after that are you encouraged to go to Sylvalum and able to actually survive a single enemy attack in that region. So while FFXV might give players more tightly defined boundaries set by the situation in the story, Xenoblade X's freedom really isn't all that much more free since aggressive & deadly lvl 50 enemies & other impossible to do content will make sure that that players will keep away (and if they don't the game will do its hardest to MAKE the player stay away)
Xenoblade X's focus IS on exploration (that's basically all you do in the game, fighting filled exploration), but that doesn't mean FFXV's exploration is just an afterthought when it gives a bit stricter boundaries to the player set by where they are in the story.