Great resource Glen…exactly the question I posed to @LateJunction . Once you get an idea of the process you can use it in all color managed apps to break down how they are doing things…
That is a great diagram.
One key thing here is that DT also has a histogram profile. Currently this is what provides the data for the histogram output and the picker values and gamut data.
Normally that would be derived from the working data directly at least I would think so to be accurate…How ever DT processes it after the display profile which is often a lower gamut color space. This can introduce some issues that are discussed and partially resolved in the links I provided above… It has been suggested that the only accurate way to confirm if you are getting a clipping artifact from your display profile is to set it to linear rec2020…so in effect match your working, display and histogram profiles to avoid any transforms and see if the histogram data changes…your image will not look correct on the screen but the gamut data would then be accurate…if there is a change but it is minimal then you can likely use your display profile without checking this however if not currently I think it is the only way to truly assess gamut issues esp ones related to saturation…
I think there was some discussion of trying to reorder this but no solution that would not break previous edits was evident at the time…
So its a test that everyone using DT should try just to confirm if there is any issue with the current display profile they use as it pertains to impact on the presented histogram…