There are a few model airplane references out there with BS like that between the covers.

100% efficiency? I think not! What is missing is the definition of that pitch number and how it relates to the airfoil used.

It seems most of the hoopla over the airspeed versus rpm and pitch has to do with the oversimplified definition of pitch used by (most or all?) model prop manufacturers. Pitch as listed is typically not measured from the airfoil's zero lift angle but from the chord line or a datum line parallel to that. Cambered airfoils generally have a zero lift angle less than 0 degrees AOA. Therefore a "zero pitch" prop with a cambered airfoil (versus non-cambered or "symmetrical") will still produce forward thrust when rotating, since it's true pitch is still positive. Therefore, one manufacturer's 6" pitch prop may have a different true pitch than a 6" pitch prop from another manufacturer. Pitch numbers are certainly important, but if the manufacturers use different airfoils, it is possible to be mislead by comparing the numbers directly.