But then you're using other methods, you're not using the ID as tracker. In fact if you just remove it, it eliminates this entire discussion.

The trick is to combine it all, which is what MS is doing. For example your MS account stores any GDIDs that you've logged in with.

If you use a different identifier to track changes in a GDID/machine-id/etc., that means you can continue tracking using mainly just the new machine-id, but you should always keep trying to correlate it with other things in case it changes.