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.