Fun story, when my ex and I split a few years ago, I wiped all connections of my Microsoft account to the machine I built him.

Last week, when I logged into my Microsoft account, I had an extra machine with a funny name. Checking some logs, sure enough that was the hostname he gave that machine. Realized what had happened, refreshed the page, and it was gone.

The URL parameter for these devices in the Microsoft Account page is the GDID. So the Microsoft Account page showed me a GDID of a device I unlinked ~4 years ago. (And I'm slightly obsessive, I check on my Google/Microsoft account every other month.) Gooood job Microsoft.