^^^^Because those were the only "official" Mac cards sold that were issued as "Mac Edition". See this from Nvidia's web site concerning Pascal Cards.
https://blogs.nvidia.com/blog/2017/04/06/titan-xp/
Posted on 04/06/2017
View attachment 719060
Lou
That's exactly the point. Only those card are the official Mac card. All other cards are in grey area. Web driver also supported for those iMac, Macbook, etc, but in beta support. Those are also official Mac GPU, but even that, Nvidia only willing to officially call it a beta support. It's really hard to say that the Pascal / Maxwell support are not considered beta. In fact, by considering it can't provide 100% support in MacOS (e.g. iBook bug), even that's not Nvidia's fault but Apple's fault. Call it a beta driver make more sense.
As fas as I know, the web driver provide much better support for those iMac, macbook's GPU. Less bug, more mature, but Nvidia still call them beta support.
In fact, they clearly mention it's beta support for Maxwell card. Even though they didn't mention this word in the Pascal post. But it's hard to believe that Maxwell still beta (they never officially upgrade the Maxwell support from beta to official), but Pascal is official. Also, clearly the Maxwell driver has better quality than Pascal at this moment.
https://blogs.nvidia.com/blog/2015/08/31/mac-driver/
posted on 31/08/2015
Anyway, no matter it's beta or not, it's the only driver we can use. But for me, unless Nvidia update the driver download page to clearly put these cards in the official support list. I personally will consider that's still at the beta stage. A blog is just a blog, not as formal as the driver download page. The blog is more for releasing information, marketing, public relationship, etc. Not for precise determination if the Pascal driver are official or beta. Lack of the word "beta" in a blog post doesn't mean it is not beta. If we straightly follow every single word in that blog post, and believe those words covered 100% the fact, then only TitanXP is supported, not any other Pascal card. Any Pascal GPU's are not belongs to the "award winning" group has no support at all.