The thing is, before I added this line there was only the original vmdk file, even after multiple sessions. It is only after that change that the other ones appeared.
I notice many crash logs for this VM.
Update:
I was reading about the various snapshot commands at the site you recommened (sanbarrow.com) so I decide to try:
snapshot.action = "autoRevert"
This worked perfectly without adding the independent-nonpersistent line, which gets deleted anyway. The first few times I tried it, the VM would suspend, like it did with my XP VM, but now it powers off and reverts to the snapshot.
BTW snapshot.action = "prompt" also works just like in Workstation.