I’m not sure how long it has been since Retargeting was made avaliable, but that is precisely what allows you to interface different skeletons with the same blueprint. As state originally by others.
The reason for the constrain to 1 skeleton is the possible divergence of bone tracks.
how can the engine blend bone tracks if a bone track exists in one animation but bot in the other? It cannot.
Hence, all animations are required to utilize the same skeleton, which forces the same bone tracks to be present.
.25 gave us superior debugging, but I don’t think they made changes to the core of the system…