The osu!mania Ranking Criteria, under its difficulty spread section, includes the following rule:
Note: I'm aware that the latest o!m RC draft doesn't include this, but that's still under discussion.
Each beatmap must have at least 2 difficulties and one of them must be Easy/Normal. Marathon is an exemption
Regardless of whether this rule ends up being a contradiction with the general RC or not, as the removal of the 2-diff rule has been brought up for discussion again, it is addressing stuff that concerns and is regulated by the general RC, and should be removed from the current o!m RC.Note: I'm aware that the latest o!m RC draft doesn't include this, but that's still under discussion.