A Microsoft file hosting and synchronization service.
Hi 5ilverorange,
I understand your feeling and read all your reply carefully. As you can see in the article: Sync files with OneDrive on Mac OS X , Turn on Finder integration part. If you turn on the extension, you will see sync status from overlays on files and folders in Finder. I have tested on my side; OneDrive will not stop syncing if you stop the extension. As pre your screenshots from Activity Monitor, the OneDrive Finder Integration take high CPU usage but not OneDrive App, so please disable it temporally and check the result.
Besides, from the activity Monitor, the Finder and distnoted take the most and second most usage of CPU. Does it stop running if you turn off the extension?
Regards,
Clark