Yeah me neither, nothing really points to it being a joke. They said, "thanks Neogaf for the memes" but that's it. Sounds like they just wanted some fan interaction if nothing else.
Here's the breakdown and where the "joke" fits in:
-FFXV Twitter shows off how they're using photogrammetry to create realistic props for the open world such as the rock assets.
-Also, they tweet an older video showing how they have been using the technique for a while and how some of their real world location scouting has already been realized in Episode Duscae.
-The internet interprets this as mismanagement as they're going to such great lengths to get pretty rocks late in development. This overreaction came from a position of ignorance on the process as photogrammetry is an extremely easy and time efficient process compared to hand sculpting and texturing all the assets their creating from their field work(again not just rocks).
-FFXV Twitter "jokes" that people really love rocks, because they are so fixated on one aspect of the previous tweets. They effectively refused to engage in a conversation about their game development timelines with people not in the industry.
Extra context: The FFXV marketing cycle had been in a self-imposed lull due to the development shifting to focus on all aspects of the project at once. Typically game devs have at least one or two parts of the game that they keep polished to a further extent than the rest of the project so they can show it off for trade shows etc. In extreme cases, this can cause detrimental effects to the development of the entire game (see the many public changes to Bioshock Infinite throughout its development as a result of focusing too hard on public demos).
The FFXV team decided to mitigate that by staying quiet until March when the game will be largely complete. The marketing department decided they could not afford to be quiet about the game for that long, so several efforts have been made to maintain communication with fans, albeit a drip feed, via their twitter account and forums.
My take: Square's marketing should stay quiet until March. Even though they are well intentioned, their drip feed leaves a lot of room for vocal and impatient fans to turn everything they say into something negative.