What you say about HairWorks optimization is true, but you can't hold the fact that AMD has failed invest against NVIDIA. Look at it this way, if TW3 hadn't added HairWorks everyone would have the static hair meshes. As a game developer I would integrate HairWorks so that I could shine on compatible platforms (albeit I'd probably disable it by default for AMD, instead of having a bad first experience).
It's a pity that the consumer gets caught up in all this. Who's to blame is a lot more difficult to determine than most people think. Purely in terms of graphics cards, NVIDIA has great post-sales support. If I buy an NVIDIA I know games will run well on it because NVIDIA makes sure that they do. This is a pro-consumer post-sales service that I get at absolutely no cost. They are also running up against AMD users in the way that people describe in the comments of that article.
It's not a black and white situation but AMD is certainly not helping in even an insignificant way. AMD customers should be demanding answers from AMD before (not in exclusion to) they demand answers from NVIDIA.
TressFX does the same thing, but AMD worked with Nvidia to optimise it for their GPU as well, so everyone's happy. This would have been objectively better for the user, if you disregard the money the devs received from Nvidia for implementing HairWorks instead of TressFX.
Your point about hardware differences makes more sense; I don't expect AMD to admit that their hardware is simply not as suited for the task as Nvidia's is.
Open Source drivers for NVIDIA suck due to lack of documentation. If AMD has a difficult time than Open Source drivers are doomed.
AMD does make good hardware and it has traditionally been a good company. The issue is the lack of a standard. I don't like non-standard solutions with closed code or hardware.
Of course, I may be exaggerating and government interventions are rarely any good for consumers. It would be better if we, as consumers or developers, would acknowledge such abuse and punish such companies with our thoughts and wallets.
So no, AMD not having access to that source-code is not OK, plus AMD shouldn't have to patch their drivers for that game, because such a practice has far reaching consequences, affecting indie game developers (Nvidia won't patch their drivers for indie games that aren't as popular as Witcher 3), or any operating system that isn't number 1 (which on the desktop means anything non-Windows).