Yea, none of these explanations explains the fact that spiking a ball that is snapped IS stopping a moving clock. Even if the clock is stopped pre-snap, snapping the ball starts the clock. Thus, you're still spiking a moving clock.
That's the problem with your argument. It wasn't a moving clock. It was really a boneheaded play by the Saints. They should have known the officials ruled Landry out and the clock was stopped. They could have huddled and run another play.