When did you run into this? If I remember correctly which is questionable
I have rented unrated movies there and the 3 Dragon girl movies that seemed to be unedited and could have been X rated or maybe it was unrated.
There were stories about this some years back. Blockbuster does not now, nor have they ever, directly censored films themselves. That would have been illegal, as they are not the copyright owners. However, anyone can avoid carrying films that they deem to have objectionable content, and
supposedly in the past Blockbuster reportedly put pressure on movie companies to release edited versions of some of their films.
From a very superficial search, I have found nothing to determine the actual facts of the past. But they do not seem to be doing any such thing currently, and have unrated films, like
Y Tu Mama Tambien, which they could have only in the
R version if they wanted it (as the film has been released both ways on DVD; it was released in theaters in the U.S. with an R rating, and is with added material in the
unrated version). Usually, in such cases, when the MPAA board first saw the film, it was likely such that it would get an NC-17 rating, and in order to avoid that, the studio edits the film in order to get an R rating for theatrical release, as many theaters will not show NC-17 films, and many people will avoid them. Really, having the MPAA system results in censorship of films prior to theatrical release, which has nothing to do with Blockbuster.
But, of course, the choices that they made in the past for what to have available and not available would likely impact what the studios would do, when Blockbuster was the biggest rental store. I believe in the past, Blockbuster tended to avoid unrated versions of films, but I have no means of verifying this one way or the other. It is irrelevant to what they currently do in any case.
Of course, I have no way of determining whether there are local or regional differences in what they offer in individual stores. It is possible for a company to not have unrated films in some stores while having them in others, though I have no particular reason to believe that Blockbuster is actually doing this either. And, of course, they may have more than one version of the same film in one store, as some people would prefer to have an R rated film to an unrated one that, if rated, would be NC-17. So even visiting stores and finding an R version would not mean that they necessarily did not also have an unrated version.