Actually, the developer Orcm has gone on official statement saying that he prefers for futas to be "ambiguous" as to whether or not they have a pussy or not, so in game they will always appear to only have assholes. Futas who are futas from the beginning are like that as well, it is kind of retarded because his reasoning is "some people define futa as shemales with no vag, others as hermaphrodites without testicles, so I let people make their own interpretation"
This is kind of strange, as sissification essentially makes (Admittedly stereotypical female attitude and submissive) shemales already, so Futas are just a version of that, that is less inherently submissive and overtly bimbo-ish. That being said, I personally don't care because I'm into shemales, but his reasoning doesn't really strike me as logical in this regard.