technically calliope could be correct about gender-restricted classes, just not in the way she thinks--if there is exactly one muse and exactly one lord that exist in all of paradox space (likely, given the level of impact their powers have on uhhhhh everything ever) by definition they are both exclusive to a single gender

That is definitely a possibility, given how weird Muses and Lords are, although then the ‘exclusive to a single gender’ thing would be a completely pointless statement, as they’d be reduced to a single individual. The way Callie mentions it and how they appear, even if they are indeed only granted to Calliope and Caliborn, they’re classes built in within SBURB’s Classpect system in itself.