No - there is a huge difference between "this AI created this image" and "this user did it" - the first we need more of, and the second is a big privacy concern. The article does not say anything about identifying a user.
Article literally says it adds a guid, not a binary field indicating that the image is ai generated.
a GUID isn't an indicator, it's a fingerprint.
so unless you want to draw a distinction between 'user' and 'machine' , yeah it is for identifying users.
to believe otherwise, especially with Microsoft involved, would be incredibly naive to their history.