If you have a penchant for uncovered, orb-shaped body parts, Nintendo isn't going to be in your good books.
Nintendo obviously has a pretty family-friendly image for the most part, so you're unlikely to find scenes of a sexual nature in a Mario game. However, with the Nintendo Switch, some more risque games have made it onto the platform. According to one indie developer though, outright "uncensored nudes," won't be allowed on the eShop.
Publisher Gamuzumi recently confirmed that one of the games it's publishing, Hot Tentacles Shoot, would not be coming to Switch for the time being (thanks, Nintendo Everything). According to Gamuzumi, the reason for the game not being allowed on the eShop is that "obscene content could damage the brand and infringe its policies."
A censored release of the game is planned to release on the Switch, but Gamuzumi does not it likely means other developers will be affected too.
Hot Shoot Tentacles is an 80s style shoot-em-up, where defeating bosses essentially removes tentacles that are covering up images of scantily-clad women. Oddly though, topless nudity has been allowed on the eShop before, most notably in The Witcher 3, which features sex scenes with fully topless women, as noted by Kotaku.
The Witcher 3 sex scenes are censored in the Japanese release of the game, though are easily viewable elsewhere, so it's a bit unclear what Nintendo's actual stance is on the matter. AAA games are often given a pass when it comes to these kinds of situations, where indies have to face the brunt of the policies, even if it is a game where you shoot spaceships to see "uncensored boobs."
It is obviously a private storefront at the end of the day, and if you're desperate to play the game it is available on Steam, though Nintendo being inconsistent isn't exactly surprising.