I understand your point and for sure agree with your explanation .
Maybe it is the downsizing method that causes this ... i do not know .

I work from 16 bit ( Pro Photo ) PSD from C1 or from 16 Bit ( wide Gamut ) Tif from DPP .
Once finished with PS work i downsize with a script someone has created or go via File - Automate - Fit Image to get the desired output size .
And as stated before i do not have that " issue " with the clipped histogram , only if the PSD/TIF is borderline on both ends i might get that .

Cheers Andreas