Is it, though? Can anyone compare/contrast the 2 designs? Just because the same people work on them, doesn't mean they're necessarily related (Alpha vs ARM).
Dave Cutler worked on VMS and NT and as far as I know NT is quite different, for example.
They were not very different under the hood. In fact, many units within the OS were similarly/equally named. The UI was a different beast all together and I remember the UI crashing in WinNT 3.51 while the kernel and services were happily chugging along.