It is to me. When I buy a car, I do not leave a 1 star review stating "This car is not a motorcycle; extremely disappointed.".
That's exactly how these comments being made sound to me. Nvidia is very clear that they only support their proprietary driver, and they deliver on that.
I have many GFX card from all vendors over the years, and I've had to send one back because the vendor wasn't honest about things like that.
Do I wish nvidia had good open source drivers? Sure. Do I blame nvidia for these not existing, not really. That would be like blaming microsoft or apple for not making all their software open source.
I do however blame vendors that do advertise good open source driver support that ends up being crap.
What does any of this have to do with nvidia buying or not buying arm ? Probably nothing.
What nvidia does with their GFX driver can be as different from what ARM does, as what Microsoft does with Windows and Github.