Unexpected reboot for already-installed updates

I have auto-updates disabled on my desktop via group policy, because I need to control the timing of updates and the timing of reboots.  I handle these manually once a month after patch Tuesday when I can be in front of the machine.

The last time I installed updates was on April 26, at which time my machine received 2026-04 Security Update (KB5083769) (26200.8246) and 2026-04 .NET Framework Security Update (KB5082417).  I rebooted the system manually and completed the update installations.  There is an event in the event viewer corresponding to this reboot sequence at 10:14 PM on April 26, so I know I didn't forget.

Windows Update reports no updates installed between April 26 and today.

This morning, I came into my office to find my machine on the login screen again, as though it had rebooted.  I assumed there had been some kind of hardware or power failure or system crash, but instead, I saw that the system had been rebooted again, at 03:29 with the message in the event viewer

The process C:\WINDOWS\uus\packages\preview\AMD64\MoUsoCoreWorker.exe (MYMACHINE-I9) has initiated the restart of computer MYMACHINE-I9 on behalf of user NT AUTHORITY\SYSTEM for the following reason: Operating System: Service pack (Planned)
 Reason Code: 0x80020010
 Shutdown Type: restart

The problem, of course, is that no service pack was installed between April 26 at 10:14 PM and April 28 at 03:29 AM.  The Windows Update history has no record of any updates installed after April 26.  The updates on April 26 were fully installed including reboots to complete the installation.  There are no event logs from WindowsUpdateClient indicating otherwise either.

So why did the system reboot my computer this morning?  Is there a way to check to determine whether it still thinks it needs to reboot, even though a reboot has already been completed?  I can't have this desktop machine randomly rebooting when I can't be in front of it.