I haven't used any such tools on this computer. I checked the Task Scheduler, and I don't even have the "PowerShell"-folder inside Library->Microsoft->Windows.
In my case the updates were happening as a hidden background process without my knowledge. I was almost certain this wasn't the case until I saw it happening via Task Manager. WinGet is a first party package manager which is likely installed by default (it is closely related to and comes with the Microsoft "Desktop App Installer"), and even if the specific method/task which might be automating updates is different it could still be happening.
While WinGet is just one possibility, it might be the most likely in terms of one which might be happening without user intervention given it's low level connection to Windows itself & the fact that this just started happening for both of us recently. Type 'winget --info' into a terminal or command prompt - does it show useful output? If it's installed it should show a list of directories it's using, including for logging, if so open the Logs folder and check to see what's happening.
What Neil said is also important, it could be some form of managed updates involving that or some other package manager, which might be more difficult to figure out or control if group policies are involved.
Lastly, what I said about file timestamps and the Event Viewer logs still stands. Event Viewer should at the very least show the date/time at which the Start11 V2 service gets activated along with it's installation (although it might be difficult to find given the sheer number of entries) - this can be used as a pointer to find out when the updates happen, which made it obvious in my case a scheduled task was likely involved which could be easily pinned down.
One more note: Start11 V2 appears to have been first added to the Winget repository 8 days ago which directly corresponds to when the download first occurred for me on January 9th, I'm not sure when it first started for you but you also imply that it's a very recent occurrence.