So, because of all this bogus metadata talk I compared nvidia drivers 385.28 (red) and 418.81 (yellow) simply by running a 4000 nits metadata grayscale sweep in HCFR.
TV is a LG C8.
As can be seen in the attached picture, below 450 nits there is no difference but above that the roll-off is much smoother with the correct metadata (385.28).
Using windows HDR produces the same bogus metadata result as 418.81.
I really hope this will get fixed soon.