Ok, I rewatched that scene to see how things really went
Justin does pull away but it's because he's kidding about paparazzi being there so Ethan has to be careful
but the scene is actually a positive one for Ethan and Justin.
Of course I think Justin never loved Ethan as he loved Brian, but I don't think there's really a body language that tells us Justin is not into Ethan. The kisses are different just because they're different couples and Brian and Ethan are different people. Of course Brian is generally more passionate so the body language comes out as more passionate. Also, I have nothing against Fab Filippo, but even though he's cute, Gale is much sexier and that's something that contributes to how the scenes look