As you can see here, those renamed users do have global userpages in their new names. The system however identifies that the redirect is broken, so it lists it in Special:BrokenRedirects. This confuses bots, which mark the page for deletion.

To avoid bot accounts to be blocked for this, Special:BrokenRedirects should be able to know if the page which is redirected is to a global userpage, and if so, then not list it at Special:BrokenRedirects.