I think the problem is that "it's only placeholder" was used pretty extensively during discussions in the run-up to GT5, 6 and Sport to stifle debate. You can't talk about anything if everything is subject to change, and it certainly becomes impossible to be critical of any aspects that you think might need work.
It's far more reasonable to assume that anything that appears in the officially released advertising or media is at least intended to represent what will be in the final game. If they change it, cool, but if it's being put in front of potential consumers I think it's totally fair to assume that this is what the game will actually be.
If they're showing trailers with janky AI, then I think that in combination with their 23 year history of unspectacular AI in their games is more than enough to come to a reasonable conclusion about the current state of the AI in the game. Polyphony may be making noises about machine learning, but Forza Motorsport has been doing that with Drivatars for like, a decade. Poorly as well, I might add, so machine learning clearly isn't some magic bullet that gives you magnificent AI.