Maybe a caching / cookie / partial refresh thing but:
I have two lists in one site
Both lists have an own PowerApp associated (through Customize button in edit form)
When I open New form of list A for first time it is showing correct PowerApp A, BUT when I immediately switch to list B it shows the same PowerApp that is only associated to list A. List B has its own different PowerApp and when I refresh a few times it will eventually show PowerApp B.
I'll see if I can add a video for reference if unclear.