If you use pre-provisioning with Intune Autopilot, Microsoft may use one or more fake pre-provision accounts which may need to be licensed for your Intune if you use UPN licensing.

This user is typically “foouser@your-mail-domain” and may not be the same as the UPN you’re trying to get licensed for.

You can see this string by investigating hklm\system\currentcontrolset\control\clouddomainjoin\joininfo\(*some alphanumeric key*)

An example from the blog https://call4cloud.nl/2022/09/foouser-meets-the-cosmic-autopilot-user can be seen here.