doug> I was gonna reply, but my desktop Linux rebooted - oops my bad..Drafts to the rescue.
Guess why my desktop rebooted? I was messing around trying to peek at Quit options
........musta highlighted Shut Down. I caused my own black screen of reboot/death! Ha.
But I had Mint/etc updates waiting. I ALWAYS have them waiting. (except just now/rebooted).
Gory detail/thoughts on your Q?:
I can't think of a reason to fea of your current favored Choice2 below:
Choice1:
"reboot required" --> shut down now. Fire up tomorrow.
OS patches ...mmm, nothing eye catching in the list that pops up
on GUI/Mint/MATE on behalf of UpdateManager (not SoftwareManager),
the bugger that pesters me, adds popups 1x/day or such...
,,,As you sneak-away/ponder "ready to reboot/shutdown?"
you wonder when you feel like peeking at the update list.
Choice2, (via any method ...click,allow,bless your imminent death,
via anything like GUI choice Quit->Shut Down
which probably invokes something like "shutdown --?" couple flags like
-h
The same as --poweroff, but does not override the action to
take if it is "halt". E.g. shutdown --reboot -h means
"poweroff", but shutdown --halt -h means "halt".
Oh, gory! Anyways, the answer seems (always?) dependent on time/patience.
Pardon the tangent now, if you're here, I'm amazed:
"poweroff" however that really works with "shutdown" or other trick,
might vary....... motherboard/etc might get a signal and take a real nap..
If you have hard disks, not SD, beware a days-long sleep ...sticky platter shaft/bearing...
(choice3) If I was feeing Totally Watchful, I'd reboot, watch...Log In, ...then Quit.
Inevitably=-> "Log In", and boring.....see what Update Manager sees in its playpen.
Debates,topics, questions could easily continue if interesting!
---the bottom line might be
what's the processes(session, service?) of greatest interest for you on your (desktop)?
I leave/let a 2010 Dell Opti w Mint 20.1 sleep on its own,
SanDisk HD/root good since 2018/2019?. 500gb/disk1 (disk2 for "your data" helps for long life).
CPU Fans still orig and quiet, a miracle! --doug