Perhaps this segmentation has some contractual clauses that effectively bans companies from buying gaming cards to mine with? They're not enforceable everywhere in the world, but if it covers a big chunk of the cryptomining world then that's probably good enough. That way they can charge a premium for mining cards.
Nvidia already did this once before: their driver license specifically prohibits you from using GeForce cards in datacenters. Only Tesla-branded cards (no, not the car maker) are licensed for use in a datacenter.
The license is pretty much unavoidable, even if you're using Nouveau, because the cards won't work at all unless you give it's power-management processor an Nvidia-signed binary to run, and Nvidia won't sign Free replacements for that binary.
Mining operations are pretty fucking sketch for the most part (in china they just straight-up steal electricity) and miners won't care about terms of service in the same way that a billion-dollar corporation would. You're not going to get ratted out by the secretary and have all your assets siezed, short of requiring an always-on internet connection and ratting the user out for mining (which would be incredibly unpopular) there's not a whole lot you can do, it's all possible to do stealthily.
