Hello,
I also don't understand why I need to completely download and reinstall Windows 10 as well. There is an issue with the update itself. Will the Microsoft team be taking a closer look at the release? I can advise when the update fails it does rollback the update altogether. I just went ahead and paused my updates for the time being.
Also, I have seen the tips on restarting / resetting the Windows Update via an elevated Command prompt. That did not work as well.