DF is in charge of the article and they call the shots. But, why would you want the abstract to be out there before the presentation? You get way more publicity for something that's earth-shaking when it's either in an article in a journal, or presented at the conference -- not just dumped out there in an abstract.

In other words, embargoing the abstract is good all around. Except, of course, for those who find themselves short when it's released.