I believe the term is null-crotch rather than smooth-crotch, actually! :3c 'Cause i see some fuzz down there~ So cute!
Learned a new term I'll have to keep in mind whenever someone complains at my taste for gender-neutral designs. Sometimes you don't need to ruin good art with sexual definitions (in my case, I usually give animals a free pass there since they're naked by default).
Recall noticing this one cartoon based on the Old Testament that managed to sneak in a nude Adam and Eve while not making an effort to conceal them too much as to show how null-crotched they are.
http://youtu.be/3WfX49oQTzQ?t=15m30s
Link
Dibs
gulp XD