I've sucked a lot of cock and didn't do as well as that guy's "first" time. Takes a lot of practice to take cock so deep down your throat. So, I think the girl realizes her BF is a natural born cocksucker or has sucked a lot of dicks before. Maybe even that handsome stud's cock many times, because they sure looked altogether too familiar with each other! And it was all a ruse for the cocksucker's girlfriend. It probably worked too because can your girlfriend respect you if she knows you are a cocksucker? Doubtful, especially since she has this feeling he'll be going back for more of that luscious cock! She'll be asking many questions when they get back home.