Add new worlds/ and World offical types to databases

[MariaArvana]

They'd also need to upgrade the game's age rating to accommodate such a move...which is something I don't see happening.

On a technical level it wouldn't. A mature server by itself isn't bringing any content to the game that would force a re-classification by the ESRB/etc (as anything it does bring would be purely player-interaction related, which isn't rated by the ESRB), which only rates the actual game-dev content of the game. Hence the little disclaimer of 'online interactions not rated by the ESRB' they tag on to online games.

Mollusk's reasoning would be far more accurate here, where trying to explain why a server with the tag of 'mature' exists would be a PR nightmare, or trying to explain that 'mature' means much more than just adults rubbing against each other.