How about an actual test result to muddy up the water.
15 HP Yamaha 2 stroke, 14 ft fiberglass boat yielded 5500 RPM with 9.75 pitch prop and 6,000 with 9 in pitch prop. That 3/4 inch difference in pitch yielded 500 RPM difference which agrees with your observation.
Oh, and I am one of those not in his right mind. All my 2 stroke motors below 18 HP have been normally run at WOT. They are tools to me which are kept in tip top condition, as I am a fisherman not a pleasure boater
The larger motors are run at cruising speed.
I am a prop nut who changes props for different purposes. My rigs have one prop for heavy loads and another for general purpose. I like to get all the goody out of my motors without straining them
When we sold the 15 HP Evinrude, it had three props for different services, all of which were useful from a light inflatable to the 14 footer with grandchildren aboard. Someone stole the fourth prop which was a barge prop used when the motor was on a large boat as an auxiliary.
Come to think of it, we have three props for the 30 HP Merc. One is fine for a heavily loaded boat, the other is for my wife and I fishing, and the third ended up as a disappointment good for high mileage but not much else. Too much diameter and cavitates easily.