Why is it, though? I mean, we look at Alexandra Trusova - She gets full levels on all the elements and ... well, is somewhat lacking in skating skills and presentation but not absolutely dreadful. She has more quads than any 13-year-old boy will likely ever have. We look at Anna Shcherbakova - She gets full levels on all the elements and also has a quad and her presentation skills are something else. Why can these girls do this? The quad thing hardly works as an excuse considering they also have been practicing it, and actually have it(Or Shcherbakova had it, hopefully she regains it).
Well in the first place there are more girls who skate or start to skate so it makes sense as you draw from a larger sample so there's more chance that you come across someone who developes so well and stands out like Trusova, someone exceptionally talented. The number of boys who enter figure skating is much, much smaller - there's no pressure either on, not so much competitivity either. You don't need to bother as much and you're not pushed by other competitors. Girls also develope differently than boys, till they hit full puberty the physical capability is approximate - there's no clear biological power advantage yet, and with certain areas like mastering those more fine, subtle motor skills (like balance) they actually outperform boys of the same age. Boys just stay clumsy for longer. Girls also hit their maturity earlier (ok, this one can work as a disadvantage, but they may gain various skills earlier on). That is not just figure skating related phenomenon, you can relate to it and describe that using different, even proved by science examples.