Hi, dssds1
Thanks for your reply! Merry Christmas!
It should be explained that we are only support staff, not Microsoft employees and developers, so we can only provide solutions according to the existing functions and features of Windows. Regarding the display problem of Windows update cache, the results obtained by our test are the same as yours, so I think this may be related to the design of Windows. I agree with your point of view. As a user of Windows 11, I encountered the same situation as you when using Clean disk. You can check and compare whether the space of C drive has increased before cleaning.
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Best Regards
Nicholas.Z - MSFT | Microsoft Community Support Specialist