The Windows Media Creation tool allows the user to place the operating system and other files on a storage location and then use it. A full clean install requires the user to boot from the media that was created, whether it be a USB device or a DVD. Booting from the media will then allow you to install the new version of the operating system and it some cases, some of the drivers. It doesn't keep any of the other neat stuff you may want to save.
In your case, it sounds like you ran "setup.exe" from inside the USB/DVD media. In that case, the installation saves your files and many of the previous settings and only installs the new items from the new version's installation set. In fact, it is much like a "repair" install except any new operating system files from the new version/build are now going to be installed. Damaged files will be replaced but if there is a new file version to replace an old one, the new one will be installed. In the example you've mentioned, NET Framework 3.5 will reinstall itself and because NET 4.8 is new, it will also install itself.
Hope this helps.
Grif
In the past when I did a ‘clean’ install, you could tell because you had to reset / reinstall everything. This time, there were a number of ‘settings’ that appeared to be carried over. Example, my “screensaver’ was already ‘there’. My log on account ‘picture’ was already there. The setting that “I” set to have a ‘large’ mouse pointer was already there. Too many others that I don’t remember now, were still there! And, yes, I did have to reinstall “all” my programs / software and do ‘most’ of my “personal” settings.
The reason for the ‘clean’ install, APPCRASH’s. . I had suspected for some time that something wasn’t right, thus the ‘clean’ install. Yes I ran things like sfc /scannow and chkdsk /f /r /x.
View reliability history shows a ‘different “appcrash”: Problem Event Name: APPCRASH
Application Name: taskhostw.exe
Application Version: 10.0.18362.1
Application Timestamp: e9bfb510
Fault Module Name: unbcl.dll
One suggestion was to uninstall .net3.5 & .net4.8, which I did. Upon reboot, .net3.5 reinstalled itself. So maybe the issue is resolved, time will tell. ‘appcrash’ shows up every couple of days.
Question? Why didn’t ‘clean’ install work via USB media creation tool? And will a ‘repair” install work? And ‘yes’ I did unplug all “usb’s” before I started.
Thanks in advance

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