Sorry for the late reply, I just noticed this now as I haven’t been on the forums for a while.
Our goal is to do everything in engine eventually. We just added the Maya plugins as an initial thing to get the tech working. UE 5.5 also introduced muscle simulation that can be used to generate training data for example.
We also are moving away from pure random pose data, but using some ROM animation instead, which is then modified to generate the final training data from. We are providing this ROM as well, so it can be retargeted to your character. I can’t make promises right now, but 5.6 might have the training data generation tools in engine.