But I dont think it makes much difference
When I was a flying instructor, I used to produce Bell 47 charts to illustrate this phenomenon. As you say, a very inexact science.
Later I flew IFR on the North Sea, and noted carefully when I flew from a clear blue sky into a cloud. I was careful to not move the collective.
Speed stayed the same. Height remained the same.Torque and all power parameters remained the same.
So I think that it is the aeronautical equivalent of that mediaeval debate of how many angels can stand on the head of a pin.
TK