A more efficient prop may have a higher load, because it transforms more of the engine's power into actual pulling power (thrust).
A less efficient prop may have a higher load, because it transforms more of the engine's power into turbulence...
I suppose that could happen, but I understand a 12" square square stick can be spun at a higher rate than even the lowest pitched 12" prop. For a less efficient prop to to have the same load it is going to have to be bigger in diameter and area. But as I said that is apples and oranges.