In the newest iteration of a time-honored tradition, grub (and/or whatever distro's treatment of it) has been finding all kinds of ways to break upgrades for 30 years. If you're on the happy path you can probably go a long time without a problem.
But when you're the unlucky one and need to search for a fix, and you're checking hardware/distro/date details in whatever forums or posts, and that's when you notice that the problems don't actually ever stop.. it just hasn't happened to you lately.
No that's not what I mean, I mean technologically, UEFI is flashed in your motherboard and there isn't any way for an OS to mess with that. You need to boot from a specially prepared USB with compatible firmware in order to change it. Your problem must have been above UEFI, or an error in your OS that mentioned UEFI.
There have been buggy implementations where UEFI is in fact NOT flashed to the motherboard and can get removed.
If he has one of those crappy computers it could be, but when I read about it happening it was entirely due to users MANUALLY deleting the UEFI files, did not happen upgrading.
But when you're the unlucky one and need to search for a fix, and you're checking hardware/distro/date details in whatever forums or posts, and that's when you notice that the problems don't actually ever stop.. it just hasn't happened to you lately.