Oh, please Crab. You certainly read his profile. Ray Prouty wasn't a pilot either (AFIAK). We all know there are many stick jockeys out there that still believe in gyroscopic precession in a rotor. Being a helicopter pilot is not really a proof of understanding helicopter aerodynamics.
Sokol, I agree with you, that the disk loading is just a mathematical simplification, but the downwash speed on a helicopter with a lower disk loading is really lower than one with a higher disk loading.
An approximation for this in a stable flight condition is:
square root(M(helicopter)/(2x(air density)x(disk area))
And that has nothing to do if you are going up or down or around the church spire.
The higher the mass of the helicopter or the lower the air density or the disk area, the higher the downwash speed.
Nonlinear speed changes in wind tunnel. Tricky. That's why they researched VRS on sleds.