Don't modern versions of Windows do the same? For example, I clearly remember that the Windows 10 installer first launches a Windows 7-like environment.
Aren't all modern (>xp) windowses just NT6 under the hood? Is there such clear delineation between 7 and 10 for example?
They're all NT, though I'm not sure how you mean "NT6"; XP was NT 5, Windows 10 was NT 10, and I think 11 is 11.