FlightDetent,
Thanks for the careful and patient explanation. At the risk of further trying everyone's patience, it seems as if the reason to shut down 2 ADRs would be that the fail-safe philosophy didn't work as well as expected in practice. If ADR 3 might have an unreliability the system hasn't detected (which I think is what we're assuming), and you left it on, it seems like you could still end up with something like a large NWS deflection early in a cross-wind landing (because the ADR thought the airspeed was low when it wasn't).
Or maybe the answer is that the NWS reverts to fail-safe mode at the first hint of trouble with the ADRs, so it doesn't matter what you shut down? Or perhaps there's something else, maybe a ground-speed input, that would prevent the NWS from doing anything too unexpected (in which case possibly keeping NWS might be a reason to keep ADR 3 on)?