[sophonX]

Maybe linux is light weight and is more modularised than Windows or macOS ? Was it the same behaviour using SSD vs HDD to account for disk fragmentation ?

Maybe somehow windows / macOS updates are linked to something in BIOS (Idk either) ?

Idk.

[capableweb]

I haven't used a HDD for the OS drive for many many years now on any of the OSes, so shouldn't matter.

It's possible I guess that both Windows and macOS upgrades something regarding the boot process, one of the Windows machine (which today went through the ~25 minute upgrade I described in the OP) is a Surface Pro 8, and all the macOS machines are obviously Apple hardware, so very likely there are firmware upgrades happening as well. It's a good guess.