In a traditional ABR-1 setup the ABR-1 bridge sits on posts that are drilled into the body of the guitar. In this modern imitation instead of mounting the posts directly into the body, they are mounted into studs which have been inserted into the body. So it went from a firmly mounted single pair of posts to posts within studs which are presumably firmly mounted. But my guess is the movement is from the posts and in an old one they wouldn't move as much. Can't run an experiment since I don't have a vintage one to check it on.