A not unreasonable assumption until you really think about it.
For one Maneiac had only one hair color- green.
EDIT: Correction, she does have two color mane. Been awhile since I saw her.
For two why would Maneiac take up the whole box art cover? That’s like if an entire box art was dedicated to Lex Luthor or something. Kinda weird. Not out of the realm of possibilities, but still. And that wouldn’t lend itself that well to multiplayer I would think unless you played as the power not-ponies-in-this-situation. But even then it’s VS.