The Bros have commented on how they dislike the movie many times during the press for Skyline. Look for interviews during that film's press run. The bottom line is that they hate/dislike the movie as much as we do but can't be so blunt about it like we can because it looks bad on them and people wouldn't want to do business with them.
If they are being honest about this, good for them. It is very adult to admit when one makes a mistake regarding their art, and the best filmmakers always own up when they mess up.
However, given the behavior I have heard from them, it seems possible they are saying this just so people who could potentially give them a job don't think AvP R is the kind of film they want to make.
For example, Jane Fonda's apology to Vietnam vets was suspected of having such motivations behind it.