Didn't you report a while back that running a HighSierra update on an HFS+ volume on an internal SSD would change it to APFS? That would tend to make your workaround a recurring nuisance, and out of curiosity, when's the last time you actually NEEDED DiskWarrior?
I had intended to follow the clone out and back procedure, but the total lack of reports of APFS issues swayed me, and I'm totally happy with it. (Not to mention that I haven't upgraded DiskWarrior from v 4.x, because I've had no cause to even think about using it since Snow Leopard.)
