Erasing MDM-linked MacBook doesn't remove former Apple ID

I'm a system administrator and I'm in charge of our MDM system.

When I use the Erase command from the MDM server, our MacBooks seem to be fully reset but the Apple ID of the old user stays on there. When:

• the new user turns on the laptop, and;
• they skip creating their own Apple ID during Setup Assistant

they see this screen:

Where the Apple ID is the ID of the old user. We don't use managed Apple IDs.

The old user still sees the laptop in their account and can Lock or Erase the laptop from Find My.

Fully erasing the storage through Recovery and re-installing macOS has no effect - the new user still gets this screen, so I'm guessing it's an Apple server-based issue rather than something stored on the local machine.

I'm struggling to figure this one out so if anyone has any ideas I'd be really appreciative!