A) considering that is likely an OEM license you would technically be breaking the license agreement. The OEM license binds OS to the motherboard which that copy of windows was first installed on.
B) Otherwise it shouldn't be to much of an issue but you would need to ensure that you boot to the correct drive. Although there is a possibility that moving Windows could cause issues due to hardware differences but there doesn't seem to be to many so it should update just fine.
Though technically he isn't reproducing the OS install, just swapping it, albeit it's still OEM..
In any case RetiredChief got it.
I've personally never seen a swapped OS drive boot on a different setup.