Gender identity and sexual orientation are two different things.
A woman can have traits which some people define as very "mascultine" (defining behaviour as such is really a pile of baloney, honestly) and be heterosexual, and a lesbian woman can be incredibly feminine. It's all over the map.
Really, there isn'ty such a thing as a "phase" in oreintation. Intead, we all are attracted to different or same genders by degrees. Very few heterosexuals have never been attracted to a person of the same sex and very few homosexuals have never been attracted to the member of the opposites sex. Most people fall a million different degrees in between.
Being a sexual abuse survivor also is far more complicated that creating a divergent gender identity.
Basically, respect your friend for wherever he is at with his own identity. It's no one's place to second-guess anyone's defintion of self.
Editor and Founder, Scarleteen
"If you're a bird, be an early early bird --
But if you're a worm, sleep late." - Shel Silverstein