Oh, yes. I'm well aware that machines upgraded to Windows 10 and then rolled back are perpetually licensed to receive Windows 10 again absolutely any time. I did this to many machines, both mine and others, way back in the first year of Windows 10's release so those machines could be permanently upgraded to Windows 10 once there was no other choice,
FYI:
https://www.askwoody.com/forums/topic/cant-activate-windows-microsoft-investigating/
There were many similar reports at tenforums.com and elsewhere of devices that had been upgraded during the "free" period losing their Windows activation.
I don't know if this is still happening or not.
I expect that the majority of folks entitled to the free 7/8/8.1 >>> 10 upgrade path took advantage of doing so during the ~8+ years it was available before the activation servers were shut down in September 2023.
Many/most of the old kits in the hands of regular consumers that were NOT upgraded for free probably may have been retired or replaced by now?
This does all seem "moot".
As mentioned several times, legitimate Win10 licenses are still available from reputable sources (with cautious research).
AFAIK The only glitch is that the upgrade needs to be done via clean install.