@gyngyn -- then you might want to speak with someone at the school
@confusedpremed12345 referenced in her post, since they rescinded an acceptance (not a WL spot) once they saw she PTE'd elsewhere on 4/30! She was accepted at multiple schools that use the protocol, they were able to identify her without her self-reporting, and they took action. Why on earth would you be able to identify WL students with other acceptances but not accepted students with other acceptances?
I think I might be correct insofar as you can't identify them because they have not PTE'd elsewhere, and that you would be able to identify them, like your WL students, if they had done so, but apparently the other schools are not requiring it, so you are left in the dark. If so, you should consider asking for my proposed fix above for next year!