So let's say it is a sexual orientation, would that make any difference to Orthodoxy? Frankly, not at all.
We are not supposed to act upon every urge of our nature. After all, it is a fallen nature. Some people feel attracted to the same sex, or feel an urge to commit adultery. The urge is there, but with Christ's help, we can refuse to act upon such an urge.
Let's not forget that whether something is a "disorder" or a "sexual orientation" in psychology pretty much depends on the way society views it. That is how homosexuality stopped being a "disorder". And if pedophilia gets declassified (and honestly, it probably will sooner or later... after all, Islam keeps getting more influential, and Muhammad and Aisha...), it will be just the same. So all I can say is that we should hold fast to Patristic view.