Well, for example the Oogie Boogie bash poster was confirmed by
Scott Gustin to be not AI after speaking with the supposed artist. Whether you believe him or not that's up to you, but I haven't seen him post anything like this that wasn't verified by Disney themselves. The name of the artist wasn't given out either. I'm assuming they don't to deal with the backlash of all the people supposedly sticking up for artists by claiming their work is garbage and AI.
In my opinion there is nothing in any of the examples posted (except for the nightmare Mickey of course) that looks AI generated. These type of renders have been done for quite a while now. We have to be careful in not throwing the artists we claim to care about under the bus in the pursuit of finding AI.