My understanding (unless they've changed it) was that a restart is a restart because software (either the OS or 3rd party software or both) may need the computer restarted to finish installing or updating stuff.
I'd heard that a shutdown wasn't actually a shutdown, though.
I mean, I use Linux but I’ve used a lot of Windows in the past. I don’t find either of them particularly more stable than the other. I had blue screens a few years ago on my laptop and that turned out to be faulty RAM. I haven’t had a Windows-caused BSOD in years. And all this talk of Windows suddenly starting an update while I’m using it, I’ve literally never had that happen.