IMHO. Only. And I know it's not for everyone, but I like kids that talk about anatomically correct bodily functions! It tells me that parents have talked about it at home & they're comfortable with the subject.

I personally think it's great he called it a penis. That's what it is! Not a wee wee or pee pee hole. Geez. These are bodily functions.
What I usually see is that it makes other parents uncomfortable because they haven't had this conversation with their child or they aren't comfortable talking about it in public. That's their own problem.
BUT, I know I'm going to get hammered on this, but I do understand keeping "potty talk" to the bathroom!
So yes it is "realism" art & I think you should be proud that he thinking so openly about it. Peeing is a bodily function. But so is eating.