I think the big issue among the CDers who don't wish to claim transmaleness as you call it (good description!), is a belief that it is wrong to be TG, as if it takes away from who they are or it makes them lesser men somehow. This comes from being socialized in a trans/homophobic world and having internalized the transphobia.** It's a shame, really. I'm in love with a CD who considers him/herself dualgender. I don't think he or she is less of anything at all! It's like being bilingual. Knowing two languages doesn't make a person any less proficient in either one! In fact, it enriches a person in many more ways than knowing just the two languages.
** For those who are interested, see the next to the last definition in the link under my signature ... also google it for more in depth articles.