You have a point, but I wouldn't call it dishonest because everyone does this. And it does matter. Windows is the defacto standard and on a PC is how most people acquire their OS. So, those numbers do count. What they don't show is mindshare. Whether people like it, want it, love it, or if it's just whats on the PC they bought.
Naturally there are those who claim 8 is a success because microsoft posted a 40 million sales figure, however we know this to be dishonest since they didn't tell us how many of those 40 million were OEM sales, microsoft was shown to be guilty of this kind of dishonesty in the past with the Vista failure so history repeats itself once again.
If the Surface was more of a consumer success, and MS is trying with all the ads, it would have that mindshare among consumers. Unfortunately I think Surface and Windows 8 missed the mark with consumers. And IMO, you can blame it squarely on the Xbox Music/Video core apps being very poor and there being no simply syncing software such as iTunes or Zune for it. Manage music and playlists is one of the primary functions for Tablets and Phones. It's not done, especially with so many IHVs releasing tablets. But in this space, they have to compete with the ultra cheap tablets and of course the iPad. This means MS needs(needed) everything to be top notch and IMO it wasn't.
Surface will do great for business, especially the Pro. That is a lot of numbers and will insure some success but in mindshare, it'll still be an iPad world and now maybe Google too. Their lack of presence in the enterprise has left them free to focus on consumers and of course price goes a loooooooong way especially in this economy.
The fact that only a couple months after release you're hearing more about Windows Blue and Windows 9 than Windows 8 apps, games, and updates is quite telling.
Edit: I'm very interested in hearing Windows 8, Surface RT, and Windows Phone 8's Holiday numbers. I think Windows Phone 8 is winning mindshare among consumers. Slowly but surely. But with the lack of appropriate software on Windows 8 for it to sync (Windows Media Player Classic is best) it could lose momentum. Microsoft foolishly thinks it can leverage its monopoly to force feed Xbox Music pass and Marketplace music sales. This will fail.