You are correct that this is not only an exceedingly rare occurrence, but one that has only happened so far on the Cloverfield (I think, it's been a while) series of Intel processors, and because Intel decided to drop support for something Windows 10 depends upon.
Unless his hardware predates the Windows 8 era, he has no more to worry about than anyone buying a computer today has, for all practical intents and purposes. If it's from the Windows 7 era, then looking at what processor it has is appropriate. I don't see any of the Intel i-series processors, which dominated the market, going out of support any time soon because they've been used all the way up through the present.
Another thing that people need to realize is that computer hardware, any computer hardware, does have a finite service life as software (not just OSes) progresses. I have an old machine with a Pentium Dual Core that can (and does) run Windows 10, but I wouldn't want to be using it now even if it were back on Windows 7 and Windows 7 were still supported. It is far more likely that most of the computers that most of us here have today will be disposed of through our own choice than because Windows 10 support for their hardware disappears.
Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363
The purpose of education is not to validate ignorance but to overcome it.