Not sure but I have a theory that it MIGHT help sales in some cases to avoid mentioning the name of a model or the shoot in certain promo material. I suspect some people just use the updates and promo material to get the names of the models and the scenes they want and then they go to a forum, filelocker, or DMCA tube to get them instead of the site.
Not giving away information might make some of them buy as they could find it harder to find the full scene otherwise.