Funny guy. But odd that this is news to you.
Anyway, this was known among enthusiasts who could change it. Nvidia HDMI drivers defaulted to limited range over HDMI on many monitors. Non-enthusiast users who don't go into settings risked living with limited HDMI range for years. So for these users, yes Nvidia did have worse image quality in some regard.
It's already been discussed in this thread. But some more sources for you.
It could happen on Displayport sometimes too:
https://pcmonitors.info/reviews/dell-u2414h/
"When using either DisplayPort or HDMI the GPU sent out the wrong colour signal (‘Limited Range RGB 16-235’ instead of ‘Full Range RGB 0-255’). This reduced gamma, skewed white point, hugely impacted contrast and simply gave everything a washed out look.
We are quite used to seeing this with Nvidia GPUs connected via HDMI as that is their default behaviour – treat the connected device as an HDTV. But we aren’t used to seeing this over DisplayPort"
And note their solution: they had to create a custom resolution. Because this was
before they added a simple drop down in driver 347.09 in December 2014. Even after that, defaulting to limited range is common so casual users can still be stuck with it.
More info here, including issues unique to both Nvidia and AMD and the Nvidia 347.09 patch:
https://pcmonitors.info/articles/correcting-hdmi-colour-on-nvidia-and-amd-gpus/
More about how it occurred for years, and how there did not used to be a simple drop down (this article is just days before Nvidia released a drop down option actually):
www.pcgamer.com/nvidia-cards-dont-full-rgb-color-through-hdmiheres-a-fix/