Alembic geometry cache animated face sets not working

I have an alembic that is a basic cube. It has five face sets on it and the face set assignments are animated. In the first couple of frames, all faces are assigned to the first face set. The next couple of frames, all faces are assigned to the second face set. And so on.

When I import this alembic into Unreal, I can see all five face sets show up as material slots. But, when I assign different materials and then hit play, it only ever shows the first material. So even though the geometry cache clearly is aware of the multiple face sets, it appears that the animated face set assignment isn’t properly being loaded in.

When I load the alembic into Houdini, it does show the face set assignments being animated, so the alembic is correct.

Does anyone know how to fix this? I have attached the alembic in question. I am using Unreal Engine 5.6.1

char_Block_Destroy2_rig_block_destroy_overlay.abc (10.3 KB)

Did some more messing around with this and I’ve found out that if the number of faces changes, then animated face set assignments work. But if the number of faces remain constant (probably more generally if topology remains constant), then animated face set assignment doesn’t work. Seems like a bug somewhere in the alembic importer