Im really confused as to how the OP’s question related to traditionalist Catholics.
But anyhow, interesting question.
To the OP about youth events, it fascinates me that you observed this trend. It is fascinating because in my Diocese it seems to be the opposite. In retreats, youth events, anything, the girls are much more numerous. Of course my youth groups are not traditional(I mean they are orthodox, but generally not traditional liturgically).
As for how in traditional circles there are more guys, it is because of the media. The media gives a false, FALSE mind you, impression that traditional Catholicism is all about patriarchy and male-ness and the oppression of females. Also in traditionalist circles, there is a lot of talk about stopping feminism, woman’s ordination, abortion, altar girls, ect. Might make some girls not raised into it uncomfortable.
But, I am both a male and a youth and a traditional Catholic, so I am talking with the perspective of being in, looking out. Somebody else might want to give the perspective of being out, looking in.