Itch doesn't have a list of what's allowed and what's not. But I've never read a staff post stating that censoring genitals in NSFW games is a reason to cancel an account.
Also, there are many NSFW games that feature explicit nudity without censorship, as long as it's artwork or 3D content, and I've never seen it be an issue.
What I would tell you to be more careful about is if you're going to charge for your games, since you must comply with the payment processor's rules in addition to Itch's rules on NSFW games, and there were some issues in that regard a few years ago.