Well said msae, and I may add that right thrust is not there to contrast P-factor also, for the same reason: when flying upright, there is a momentum towards the left due to P-factor, and thrust is towards the right: so far, so good. But if we are in inverted flight, P-factor still generates a momentum towards the left, but now also the right thrust become left thrust!

This is true at least in an aerobatic plane, perhaps it could be used to contrast p-factor in non-aerobatic planes.