This is only my take on the subject and I don't have any scientific evidence to back it up but here goes:
The word Dysphoria is defined by Websters to mean dissatisfaction or morbid restlessness. To me Gender Dysphoria is more than simply being unhappy with one's assigned gender it is more about knowing that your gender and your natal sex do not match.
I believe that gender dysphoria is what differentiates someone who is transsexual from other transgender folk, but that some people can learn to live with the dysphoria for very long periods of time.
My own experience is that I managed to function for over 4 decades despite knowing that my birth sex did not match my gender. Unlike some members of our community, it did however prevent me from entering into any meaningful relationship with a significant other - I didn't know how to be the man in the couple and I have never been attracted to men. Was I TS during that period? Definitely. Did I allow myself to want to transition? Some of the time. Did I lie to myself about the need to transition? Most of the time.
Based (partly) on this experience, I can imagine a TS who manages to cope with the dysphoria without needing to transition for a very large part of their life. In my not so humble opinion (after all what politician can truly claim humility?) it is only when the dysphoria becomes extremely acute that people like myself find ourselves faced with the stark choice between transition and suicide.
I think that what I am saying is that although some TS folk can get by with just cross-dressing, most CD'ers are not suffering from Gender Dysphoria, but truly know themselves to be men who have a feminine side or who simply like the clothing / get a thrill from the clothing.
I would not expect someone who knows themself to be dual gender to suffer from Gender Dysphoria as I understand it.
We transsexuals are sometimes accused of seeing things in almost the same black & white terms as the cis folk, but to me Transgender is a reality and a spectrum which encompasses dual gender, transsexual and other forms of gender variance.