As far as I know, it's not entirely about some purism ideal they have in mind - the difference between the two nvidia camps on Linux is the functionality you gain with both drivers, and the proprietary driver is simply more restrictive, so, yeah, I agree that they have a point.
This is the reason I know very well that my next GPU is going to be an AMD one (given that their hardware has proper open source source by that time, that is). I bought by GPU back in 2017 or 2018, I think, a couple of years before using Linux and even considering it - had I known that today's me was going to run LInux, I would've gone for an AMD GPU right away.
Even skipping the Nvidia driver debates, the AMD hardware has been a much more consistent and pleasant experience for me on Linux overall across several AMD-based laptops that I have installed Linux on. While I did manage to get things going on my desktop that has an Nvidia GPU, it definitely caused me more headache than I expected.