Item data we've exposed is by and large placeholder, and we're actually in the process of pulling it down due to a lot of reactions just like this. We thought it'd be cool to show some pre-release items in very temporary states, but it's just a matter of fact that people are going to take it at face value. Not that you or anyone else isn't able to discuss the particulars without assuming it's final content, we don't believe that to be true, but in general we don't think the discourse is healthy when it's going to be largely based on placeholder data.
To comment on your specific points though, the vast majority of affixes are simply not implemented in-game, and as the website directly queries game data, it can't pull something that isn't implemented. I'd say affixes are though one area where we want to do as much as possible by game release, but they are directly limited by when we want to finally get the game out the door. At some point feature creep has to stop, and we have to begin testing what should be (game mechanic-wise) a final product.
As you stated though a lot of the crazier affixes did not ship with Diablo II, but were added later. I don't believe that's because the designers didn't have those ideas, but they simply make more sense to expand and broaden the game featureset post-ship. You could argue that it's something that should be baked into the core experience, that Diablo III should be mechanically more complex than Diablo II at release, and the fact of that matter is that it is substantially more complex than Diablo II was at launch.
Bottom line we want as many affixes as we can get for launch, but with runestones, passives, and the itemization we're shooting for, we're already launching a game with far more diverse build potential than Diablo II.
That's right, we all whined and now they're taking it away from us.