I tried Posemaster transfer between V4 and Genesis in the latest DS 4.6.1 17. The thumbs are still not positioned correctly by Posemaster.

This is my workflow: I posed V4 in a bent over pose and then applied a hand pose to each hand, to put the thumbs into an easily identifiable position. I did Posemaster copy on V4 to copy her pose. Then I selected Genesis, which was in zeroed pose, and did Posemaster Transfer. The result is that the thumbs are still way off.