So far the only answer I have found to this is that you have to have added the actor to the level for it to be constructed at level load or else the physics won’t work in the packaged game.
So you can add the character to the scene, then possess it and modify it from there.
Thank you for posting the solution to this problem!
I’ve tried adding the whole actor versus adding a single strand of groom asset in the level, both methods seem to work (groom hair physics simulated without problem) in packaged game.