Nina is the most "mom" out of niji in which she actually tried to act like a mom to all before realizing it doesn't work and became a wine-drunk mom handling a trio of spanish/canadian/canadian-filipino brats.
For JP, I don't really remember if there's one that actually behaves or acts like a mom. I think Shirayuki Tomoe does but its probably her ASMR stuff (she felt more like a a widow/old hag who compensate her loneliness by fucking a female nurse with vomiting fetish). KR doesn't really have one and the closest on ID is Layla Alstromeria (though she felt more like a teacher rather than "mom")
But yeah, not exactly fitting the "almost all gen has it" remark on nousagi's video. That said, this does make me want to investigate further, which is very worrying.