So as an additional test, thinking maybe it was something in Calibre config files or Plugins.
I renamed AppData\Roaming\cailbre to calibre.old and my library folder from Calibre to Calibre.old.
Started Calibre and it went through the initial database creation and afterwards still shows the 7.9* version in Calibre.
If C:\Program Files\Calibre2 is gone (via Uninstall), AppData\Roaming\calibre (where config files are) is gone, and Library folder empty, basically Calibre has been completely removed from system.
Shouldn't all configuration or saved settings be removed?
And end up with a Clean install via the calibre-64bit-8.7.0.msi which was downloaded from
https://calibre-ebook.com/dist/win64?