You could certainly make that argument, but I've struggled to think of cases where processes aren't the right point of container separation.
It's quite simple if something communicates through shared memory, it should probably be in the same container. If it doesn't then that's NOT a reason to keep it in the the same container, but I don't see how it justifies the work of splitting it up....
Absolutely for anything that uses shared memory for IPC, but then you basically have threads pretending to be processes. ;-)