Camera manufacturers have been doing R&D on individual control of pixels to achive better DR for years. It is not a simple thing, or maybe its so simple that they do not see it.
The amplification of the outer circumference of pixels is turned up, for example to help counteract light loss to to the angle of incidence with wide aperture lenses. However, its a whole bank of millions that are controlled as a group.
I do not see that controlling a photosite by turning down gain to keep it from over saturating would result in a gray card effect, but it could certainly yield suprising results if not done correctly.