propeller torque is resisting the rotation of the propeller. Engine torque is generating the rotation of the propeller.
Ah yes, that might be what he's referring to.
If the propeller is at a constant RPM then these are equal and opposite
Yes and no. When the engine is rotating at any RPM, constant or not, it is creating a turning moment (torque) on the airplane. This is due to the propeller drag. If the propeller is rotating clockwise, it wants to rotate the airplane counter-clockwise.
What you're talking about is engine inertia which only produces a turning moment (torque) when the engine is accelerating (positive or negative).
Roll-Wise Torque Budget [Ch. 9 of See How It Flies]
Paragraph 9.5 and 9.6 talk about that.