Yeah, I thought this too - looking through that documentation it's exactly as described in the twitter feed. Knowing what parameters to pass to a function is not knowing what it does. Some calls may be much more expensive than others, or a certain parameter value can vastly change the expense, none of this information is visible.
I'd agree that as an end user I don't care so long as it works well - but it's still a shame that corporate secrecy is causing games to run less well than they could. They may run well enough as things are but that really isn't the point. It'll be adding to dev costs too, which means either adding to our costs or reducing the scope of new products, which impacts on us all.
Edit: I've yet to look through AMDs docs so can't comment on if they are better or not. The comments above are relating only to the theoretical relevance of good quality docs with clear information on what happens.