So they say "in the initial run". Somehow I doubt that none of the people who ran the tool and saw that didn't try just running it again and see that now it shows the space was released, or actually look at their disk usage and see the size reduced by that amount. I wonder if any of them tried a tool like Wiztree that can dig into even protected folders to show how much space is actually being used in folders like System Volume Information or the updates cache.
Microsoft may be claiming it's a "reporting error" but based on the way the new Checkpoint Updates seem to work, the previous updates WILL be retained and using up space because otherwise it would have to redownload them every time a new update is released (the way we had to download a Service Pack plus every update released after that, until the next Service Pack or Cumulative Update that included them all), meaning your updates would take longer and longer to download each time. The only way to avoid that is if they also have a consolidated package that can be downloaded instead, where they've already patched in those binary differentials, for every release, which would increase their own storage usage and effort. If they aren't going to change the Disk Cleanup tool to ignore those cached updates, or perhaps list them as a separate option to be removed with a note about the consequences, their own tools will be eliminating the benefit of Checkpoint Updates AND making updates worse for people.
Of course my Windows 10 system is showing 3.95GB of used space right now, so it's not like hoarding space for no reason is anything new. But my Win11 laptop hasn't been turned on for a couple of weeks, and with all the problem reports I'm afraid to do so unless I disable wireless long enough to disable the update service until I can perform a backup.