Refer to
Setting to 0 has never caused collisions with the phat asset not to work.
The epic team hasn’t touched anything cloth in years. And they never will. So I really doubt that now all of a sudden setting self collision to 0 makes the phat asset be ignored.
Your cull scale being set to 2 could also be part of the problem.
Also, you eliminated the phat, and you eliminated the weight paint.
Only self collision is left that could justify any vertex moving.
Unless somehow some bad cloth updates made it into the engine - about as likely as snowballs in hell.