I never played Dante's Inferno so I can't speak for that, but I am pretty sure most developers and publishers are being very careful of the Rating Board to make sure they don't get stuck with an AO rating for a game which would be a major problem for most retailers won't stock the game. An example of what can happen is Grand Theft Auto: San Andres had a scene in the game that was locked and required people to mod the game files to get to it, but because it was still the package it was retroactively rerated with an AO rating, which caused Rockstar to go back and edit the game and release a new version scrubbed of those files.
Since the rating board can be made up of people who have a clipboard with a checklist it could be that they don't want to take the risk of having the game with an AO rating because there was full frontal nudity near a romance in the game and it then becomes confused with a porn simulator.
I've already explained that I have first hand knowledge that this isn't how it works. PM me if you want to talk more about it so we don't derail the thread.
Bottom line: male frontal nudity by itself is not enough to get an AO rating. In fact, there have been games that have featured it and gotten an M rating.
That being said, I don't think it's necessary.