Thanks for posting actual information about what you are talking about, a true rarity around here.
I do not see how that changes things, unless you are trying to say it can be a combination of deviancy and mutation. I fail to see how it could be anything else.
Well, right now science is forced to include deviancy/environment with their analysis. Not committing to calling it a choice.
However, I am of the opinion that it's strictly biological, and no conscious choices are involved.
The main argument I can essentially put forth is that, no one chooses what they like.
When I watch a TV show, or read a book or do any type of activity, I don't choose whether or not I enjoy it. I can come up with reasons and try to quantify my feelings consciously, but at the end of the day, that's not a factually accurate justification for my interest and that goes for everybody. The same goes for my attraction to a female or any other subjective aspect, and the reason why I think it applies to sexual orientation.