I removed (NOT retired) one of my devices from GC web and GE, too.
It disappeared in both places, indeed.
On the other hand I still see it in GC M IOS. Not in the list of Garmin devices, because it properly shows what I do have. But in Performance under Training Status there is a drop-down list in which rhis particular device is shown as an existing, but inactive device.
1. is it a general bug?
2. is there any temporary period of X days in which all the deleted devices still show their archive performance statistics?
3. is it just me who will spend a lot of time to get rid of this earlier owned device? :-)