Hmm. In my personal experience as a teacher, parents overestimate all skills of their children if their child is talkative and extroverted. The silent children are the ones mostly underestimated. Maybe the girls are generally just more silent and therefore underestimated more?
Chaperoned a trip to a science museum recently and you can feel the shyness/weariness of the little girls to show their excitement. The boys run around doing the fuck they want bc "boys will be boys" as usual.
In my country though, it's the other way around. Girls are seen as more meticulous, systemactic and better with numbers and records.
A lot accountants and back office workers are all women. Hell, in the company I work for there's not a single guy in the accounting department and majority are women in other departments like administration, HR and Sales Operation.
encouragement and additional advanced math education would go against your argument. E.g. more parents believe their kid is gifted and more of them push their kid or explore opportunities for the kid to get better education in the subject.