^Perhaps he didn't have either. I don't think he even knew much about genitalia until his time as a humanoid where he actually HAD them and read those PADDs about mating practices.
Can you imagine poor Odo sitting there going "Doctor Bashir, what is this extra appendage doing on my body?" (Now THAT would be an embarrassing conversation for the poor guy!)
And I say this because when he's a changeling again, he has that affair with Arissa and asks if she "could tell" if it was his first time, and was pleased when she said no.