I have an alembic ROP setup with post render script that does a bunch of things after the alembic cache is done. It works great when is use the "Save to Disk" option. But the callback script never gets triggered if I run it in the background (hbatch). Is that the expected behaviour?

Same! I could have sworn I've done this before!

I, also, cannot execute ROP scripts when Saving to Disk in Background.