Thank you so much GG, for your exhaustive explanation!
This is the same effect you see when you turn on "smoothing" in the vectorscope histogram. The Smoothing feature is a good feature but I don't like as it works because, I think (and maybe I wrong ), it "false" what I am seeing. For me these tools are (should be) like a Oscilloscope instrument (or a multimeter, if you want): if the signal is a Sin wave 1Vpp@1kHz the instrument should show me that. But, I understand that here it is a bit different.
The fewer color case increments the used bins, and skips the unused bins. This sums all of the pixels into fewer bins, and the bins have higher values I don't understand this. You said: "More colors increment more bins. Fewer colors increment fewer bins."
To report something more consistent, I have changed the reported value to the "sum" of the accumulated counts for the bins reporting a pixel bar on the graph. Good explain, with the pile "graph".
I would like to do more tests about, from user point of view, to understand what diffences there are from Photography programs. I don't know what algorithm use the other NLE's and Graphic softwares, so I can not help on that. Sorry. GG, really thanks for your time! IgorBeg