One set is .MSU and one set is the .CAB which is inside the MSU too. In my test it updated Edge to 85.xxxxx https://forums.mydigitallife.net/threads/windows-10-hotfix-repository.57050/page-551#post-1627277 Edge auto updates itself to 86.xxxx
Regular Edge updates like KB4584642 are normal packages which extract one MicrosoftEdgeStandaloneInstaller.exe in WinSxS only 20H2 EP (KB4562830) has the double behavior, because the incompetent who created it chose PackageFormat="PSFX" to save 2 or 3 MB same incompetent who created last ISO/ESD didn't know that you should delete Installer\msedge.7z and empty EdgeUpdate\Download maybe in the future they will convert Edge Chromium to MSIX package
I can reproduce it when i put only x86 updates next to a x64 install.wim, or the other way around. Or when the assigned folder contains no updates (when i assign a folder for it in the script).