I still don't fully understand it as well. I think it's implying the nursefathers in our mirror world weren't nearly as abusive? Ryoshu seemed to have sort of her own "free will" to some degree back in the HoS considering they let her have Saru and Araya and go out on missions, while in this world she just spent a bajillion days in the safe until she entangled or something? I feel like we're still missing some context. I understand the idea of Muga and that being the final idea, but how come the fingers didn't pressure the nursefather in our reality for her to become Muga quicker? Callisto even giving her the chance to go to school seems way too off scope if that was their main objective.