I wonder if that's what happened as well, but it shouldn't be able to be done.

The good news is the pin only allows you to efile the return; it doesn't resolve the fact that the IRS has two tax returns claiming the exact same person, so they will still investigate.

Here are some good references:

IR-2024-294

Age, name or SSN rejects, errors, correction procedures

Protect Yourself From Tax-Related Identity Theft: Get an Identity Protection PIN