Hehe, same. I thought I had the wrong version of Win10 and that's why I was lucky to not get it. Actually the whole Win10 version thing is a disaster, with the old SP names you could at least easily check, but iirc the 20H1 is not in the version string and upgrading is either completely transparent or completely opaque...
In the "About This System" page in Settings (System > About in the Settings hierarchy or it took over the Win+X > System shortcut from the old System Control Panel) under "Windows Specifications" header the Version field there has always exactly matched the "Feature Update Release Version" including things like "20H1". Getting that from an API is intentionally not straightforward (you have to convince Windows you know about the version you are asking about), but its pretty readable there in the Settings panel if you need it as a human.
