Model Airplane News published the results of some measured true airspeeds and in-flight rpm in a model airplane. They found that the plane's speed exeeded the theoretical pitch speed by a significant percentage. The reason is that a props pitch is usually defined by the angle a straightedge would lay on the back surface of the prop blade. Flat bottom airfoils create lift even at a few degrees of negative angle of attack.
If the pitch of a prop was determined by the airfoil's zero-lift angle of attack, then your true airspeed would always be lower than the pitch speed.

Another surprising finding was that the highest engine load did not occur while static on the ground but at low flying speeds like the top of loops. As your plane accelerates during takeoff, the prop first loads the engine more as the blades "hook up" because they are no longer in a partial stall and then as the speed increases more, the prop unloads as the air speed catches up with the prop's pitch speed.