An in-place upgrade is when you reinstall Windows 10 with files downloaded from Microsoft’s servers without deleting existing apps or files. Instead, users had to select the ‘Nothing’ option, which deletes everything on their computer. The fix will be included in the Windows 10 cumulative updates released on December 8th as part of Patch Tuesday. After installing the update, you can now select ‘Keep personal files and apps’ or ‘Keep. personal files only’ in the Media Creation Tool.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-20h2-update-fixes-broken-in-place-upgrade-feature/