ABM - Federation with Google workspace

Hello All,

We are a startup with 15 to 20 users who use Macs, and all users are assigned to Apple Business Manager (ABM). We are planning to federate ABM with Google Workspace. Currently, there are a few users who use their work email as their personal Apple ID, and one user has already left the organization. If I proceed with the federation, what will happen after the 60-day period provided by Apple?

For example, if a user's email address is user@domain.com. Can I still create a managed Apple ID for that user using user@domain.com (within the 60 day period even if the user not changed the Apple ID email address), or is it only possible once that user changes their Apple ID email address?

Thanks in advance!