But I've never had an issue where something wouldn't work between the end of an update and a reboot, where that does happen on Windows. Furthermore, it has happened to me that after a kernel upgrade (on a system that did require a reboot to make it take effect), I took a couple of weeks before reboot (running long simulations), in which case I was able to apply yet another kernel upgrade or two; but you only ever need one reboot to make the latest-and-greatest take effect.
On Windows, you accumulate reboots if you wait (which requires constantly rejecting the "shall I reboot now" prompts) so you may need many; and I've sometimes needed several reboots even though I didn't delay anything.
The implementation is (IMO) really interesting from a programming perspective (https://www.kernel.org/doc/html/latest/livepatch/livepatch.h...).
Of course, one key difference here is the system never tricks you into rebooting, and rebooting for an update takes just as long as rebooting any other time, so mostly (pending additional work, as usual :b) it's invisible.
I seem to recall Microsoft exploring similar to ostree with some Windows version somewhere, so I'd be curious to see how theirs behaves.
AFAIK the only time this is the case is an update of something that can only be reloaded to get the updated version by rebooting--the most common case being the kernel.
I've been on my work Windows 10 PC for 60+hrs this week, and about the same each of the past four weeks, and five to six days out of seven the past couple years.
And never had it force-update.
You can bet the moment I took this computer home (I won't, but humour me) and tried to watch a movie it would force-update, crash, refuse to boot, and need a full reinstall.
kpatch:
I also note that Macs often require update reboots too, which suggests there is more to this.
Some Linux updates also require a reboot on some distributions. Less frequently than Windows, but still there.