Well, I was hoping for some further explanation, but for what I paid this is fine ;)
I was under the impression that DX11 (and DX10 before it) actually do a decent job of exposing basically everything that's widely supported, and in a manner that can be made to work tolerably efficiently across a range of different hardware. But I was told this by some guy from MS so maybe I shouldn't have expected him to say anything else.
Assuming it's the case, perhaps I'm just cheating by not thinking of the leftovers as useful - not because the behaviour is useless, I mean, just because if you're targeting PC, you just have to accept that the underlying hardware could be anything. OpenGL extensions could provide you with more, but support can be a bit hit or miss. Reminds me too much of MS-DOS.
But I could have been misinformed, or my supposition is simply outdated, and the article suggests that could well have been the case, in which case my conclusion would be partly bogus too.