Thanks, BJ!
I tried importing it into an existing D&D5e (newly recreated) realm to test it out before posting here, and it errored/crashed then gave me a warning that it had to go in a Pathfinder realm. I'll try it again and see if it works differently this time.
EDIT -- Nope, it's hard-crashing Realm Works (I sent a report), then providing an import report saying: "The following errors were encountered during import: Cannot assign domain from different game system". Tried with a system-neutral realm, also, with the same result.
Bug?