IgorBeg,

GG thoroughly reviewed the Histogram code to understand how it works so he could find any bugs. He says it is all working correctly as far as he can tell.

But about the following:

When the Color Model format (in Settings->Format...) is set to RGB[A]
the histogram displayed on Histogram plugins is the same as on Histogram
Bezier plugin.
If you change Color Model format from RGB[A] to YUV[A] the histogram on
Histogram Bezier no changes, but on Histogram plugin and on View Scopes
it changes. It is strange, I think.
In Histogram Bezier plugin the histogram doesn't change in the
differents color model.

we see in https://streamable.com/vr5srs that Histogram Bezier DOES CHANGE between the formats of RGBA and YUVA (note that I have set the slider all the way to Log in order to compare the same thing). You have to watch the Histogram Bezier graph specifically, but you definitely see it change. If I am misunderstanding the concern, please let me know.