First of all, you're not taking into account the fact that companies "leak" their own information ALL the time. It's done intentionally for marketing purposes and is only portrayed as a leak.
Secondly, like any company that tests a product with a closed group they limit what people can and can not talk about. Certain information has a confidentiality date on it, meaning that it's classified as trade secret until that date. And we all know what happens when you reveal the trade secrets of a large company.
But once time restrictions are met, information is fair game at that point, and doesn't necessarily have to be officially announced by the company. The only thing Rockstar, like most companies, doesn't allow is the dissemination of video media or code of it's pre-released software, and the false representation that you speak on behalf of the company. Saying anything in an official stance is libel unless Rockstar gives permission, and that too is illegal.
Edit: Sorry, quoted the wrong guy there.