As far as I can tell, OP's argument is bullshit. I did a bunch of research into max contrast displays and haven't found any reason to not use them. There are reasons to not use max _brightness_ since a bright screen can be problematic in the dark, but it's better to use max contrast on a slightly dim screen than to use max brightness with a slightly lower contrast.

There was some minor effects for people with dyslexia and high contrast, but no science-backed a11y guidelines provide evidence of reducing contrast for the general population. And since most people have crappy cheap screens instead of fancy Macbooks that UI designers use, reducing contrast makes it worse for them. Particularly at off-screen angles.

I'm not sure who started this UI trend of grey-on-gray, but it's shitty and should be avoided unless there is an intentional stylistic reason to sacrifice form for function.