So I understand that DrivePool will tolerate 2 different files with the same name & path on different disks at first, but will eventually delete one of them during the next check.
As an ordinary user, and as you mentioned it to "Christopher (Drashna)", please allow me to also recommend that this DrivePool behavior be explained in the Q4142489 wiki entry, which would be helpful for the overall understanding of DrivePool.
Once again, thank you very, very much for your efforts and all these accurate and complete answers.
By the way, maybe I didn't quite understand your status, but I'm impressed by your dedication to answering people in a forum without getting paid for it.