They can, you would be surprised just how much stuff can change and be redone during both the Alpha and Beta phases. In some cases they actually scrap entire sections of code and rebuild it from the ground up just to make it work.
Let's not forget were dealing with an entirely new development team here with a new guy at the helm that's made it a point to listen to the concerns and woes of his customers, not Tanaka who's had a notorious history of "my way or the highway" customer service quality that dates back to the early years of FFXI.
(And yes I realize you addressed this in a later post, but I already had it written up. XD)
Having Animations done and having the engine to implement those animations are entirely different things when it comes to the development of a game. Animations are done very early in the development phase, however they can't do much else with them until the main engine (what controls other engines such as movement) and all the other parts of the game is developed enough where they can establish boundaries, conditions, and effects attached to that animation, and most of that isn't fully developed till about the start of the Alpha Phase.
Considering the Alpha is still at least a month away and the footage is around a month old now the playable demo Yoshi shown may be the absolute earliest workable form of Alpha, IF it wasn't specifically created and put together as a demo which wouldn't include full features. There was a reason I underlined that, specifically because demos are a far cry from a finished product. Want an idea what I'm talking about, take any demo that was released before the final game came out, play it, then go play the finished product. I could probably safely bet 100 bucks alot changed.
In either case, to be perfectly honest there is no real win-win situation where you try to make smooth transitions and quick, precise, and responsive gameplay and they're probably struggling to find a good compromise between the two, especially when they said animation lock is going to be eliminated in ARR.






