This is true, but transmitting video at 8 bits per channel is problematic because it's too close to the threshold of perception. Any video processing you do on an 8 bpc signal is likely to introduce visible artifacts, and of course today's TVs go crazy with ridiculous video processing even at their default settings before people start playing with the brightness and contrast controls. We need to be transmitting video at 12 bpc so that video processing done at the display doesn't destroy the signal.
I tend to agree, but I would prefer to discourage television manufacturers from doing any more "improving" than they are already doing. If you're sending a signal to a display with the signal so little compressed that 12 bpc would be an improvement for post processing, then you're probably sending the signal straight from a BlueRay player or desktop graphics card. In both of those cases, I'd rather my TV not do any post processing. (Brightness and contrast on TVs are analog operations and do change with changes in bit depth. Higher brightness = turn the lights up, not a pointwise linear map)
