It's also possible that he didn't have the whole picture. When they were consulting with him and courting an endorsement there were still many, many months until launch. A lot of his information about the game will have been what the team 'planned' to make before the inevitable impact of cuts in order to hit deadlines. All that extra story they're planning on patching in for example? That was probably all already included when they were pitching it to him.
Besides, I'm on board with FFXV on paper. Sure I have some big problems with the combat mechanics and the open world and the lack of depth in the RPG systems and so on, but there's nothing there that is fundamentally unfixable. When Tabata was telling me what FFXV was going to be in the Active Time Reports, I was totally onboard just as Sakaguchi was.
It's only now, having seen the actual, final implementation, that I can say it doesn't work as part of this series. I wonder if now, if they actually had him sit down and play through the final game, if he would get up on stage and endorse it again.