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Now it looks like this problem tries to resurface from time to time. One other remediation seems to be force-quitting System Settings.
I've gotten into the habit of always restarting after an update (iOS, iPadOS, watchOS, macOS)... preventive maintenance. You'll notice small ‘uncertainties’ being resolved. Running Onyx every now and then also helps (followed by a second manual restart).

If this blessed final 26.3 comes out, I'll test the forced exit method from system settings.
 
Final release just dropped. I wonder if they addressed the quicklook window resizing, or just punted that to later?

I can personally confirm that the build #'s are different between RC and final for iOS and watchOS, so they did find "something" that they had to change for those. But I haven't seen confirmation for macOS, I don't have any Tahoe systems right now.
 
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