No I really don't think that is what morrisman means.
So when he said "propeller torque" and "engine torque".... he really meant "thrust horsepower" and "brake horsepower"?
He is talking about the fact that if the RPM is stable, then that is because thrust horsepower equals brake horsepower at that moment in time.
Thrust horsepower is equal to thrust multiplied by velocity (TAS). You could be creating 200 BHP, at a steady RPM, while stopped on the ground and your thrust horsepower would be zero.