Only thing I can think of (why they removed it from the website) is that one of Apple's employees saw some of the pictures posted in the owner's thread here (some people that seemed almost purposefully finding surfaces with particulates approaching diamond hardness to grind their watches against) and really didn't want that sort of behaviour to continue. We all know how many irresponsible journalists there are out there - once you have a couple dozen cases of people gouging their watches, you'd have one or more of them making a story out of it.
(to those that don't know - if you're at a resort where the concrete walkways and walls have a "sparkly" look to them - keep your SBSS watch the hell away from it). Other concretes can as well, but if it's fancy looking, you can pretty much be guaranteed it does have those particulates in it.
I'm not entirely sure if that's the reason. The only thing I can legitimately think of, is Apple wants to sell your product regarding features that the consumer understands. When you start getting to technical terminology with diamond like carbon coursing, it comes to the point where that's not a selling factor for most. Most to purchase the black stainless Apple Watch, likely purchase it because it's a different color and they replaced the DLC advertisement with more pertinent marketing features.
When we're discussing diamond like carbon coating on forums, it makes a difference to us. But for the typical, average consumer who wants to purchase an Apple Watch, they likely don't care about the DLC coating.
Just my opinion.