[Terr_]

I think it's likely that Microsoft is running a process to correlate "new" GDIDs to old ones, ex:

"Oh look, this one has almost all the serial numbers of components and attached-devices as that other one, it's probably the same computer with a fresh install, let's make a note of that..."

[codedokode]

They do not need this, they require you to create a Microsoft account to use your own computer (currently without a phone number, passport and selfie but that will probably change in the future).

[aucisson_masque]

But I've got nothing to hide

[Terr_]

(Aware/assuming you're being sarcastic.) I've always felt that statement reveals a serious lack of imagination, or at least a failure to apply it to the question.