I believe the vast majority of CDs do exhibit autogynephilia because sexual fantasies among the CD community is obviously widespread. And since we are predominantly heterosexual, it would be strange to otherwise believe we would not be aroused and fantasize about the woman in the mirror.
However I doubt if autogynephilia is the cause of CD behavior except perhaps in a small number of cases. This is because most CDs develop before puberty and I am sure most of us were naive about the details of the female body and sexual relations when we first emerged.
I think this theory reflects how psychology believes there must be a strong motivator behind taboo behavior and the sex drive is always the favorite suspect. Modern psychology was largely created by Freud's theories were everything seems to revolve around the genitals. This idea has lead psychology down a dead end for decades and although now largely rejected there are still lingering effects.
My other thought is how difficult it is for anyone to escape binding sexual and gender orientation together. People cannot imagine one without invoking the other, and CDs themselves are guilty of this weakness too.
The answers to causation lie in behavioral theories and the adaptation (or lack thereof) of the individual to his/her assigned gender role. Autogynephilia is largely a secondary behavior which reinforces the transition away from the assigned gender role.
