I guess people see, or fail to see, what they want to. I have this on DVD & when I watched it I thought it was pretext, not subtext...meaning that the only way the Brandon character could the influence he did over Philip (FG's character), was if they were, or at least had been, lovers.
I'll have to watch it again soon, because having watched that "Making of..." clip, I want to see if I pick up on the fact that Jimmy Stewart's character (in the original play) was supposed to also have been gay & had an affair with one them when he taught them in prep school.