Staff's Apple ID's were setup as Personal, can I move them to become Managed Apple IDs now?

I apologize if this was out here and I did not find it.

When the company was originally started they went with Office 365. When a new staff member was given a MacBook, they went and created an Apple ID using their work email account, example user123@domain.com. Since then the company has setup and started using ABM. After running into a few issues after a user left the company with Apple IDs not being removed from the device, I started researching Managed IDs. I've read multiple documents, youtube videos etc and I know once you setup the Federation between Azure and ABM anyone with an email address using your domain will get an email to change their personal account to a new email address.

My question is this. We don't want them to change the email address on the Apple ID, because it is their work account on their work device. Is it not possible to merge / change the Apple ID from a personal to managed without losing everything they already have setup?

I hope that I'm asking that correctly and making sense. Or is every user going to have to change the email address, remove the device from that Apple ID. Then log back in using their 365 Federated domain email address?

Thank you