"And I think that's because boys and their activities are seen as cool whereas girls and their activities are seen as wet."
I'm not sure that I agree with that.
Every child has a mix of interests, of abilities, of aptitudes, of characteristics. DD, for all her pink and ballet twirliness, has a strong streak of tomboy wildness - she has sought out an activity that matches that part of her, and that activity happens to be Cubs. Not because it is cool. She doesn't e.g. play football, because she's not a big fan of team sport.
Equally, DS, for all his macho football posing, loves jazz. He has found a jazz band at his level, which happens to be mainly female. Couldn't bother him less - he is doing something he enjoys. He would not perceive it as cool or wet, it is just something he likes. He doesn't dance, because he has 2 left feet and is utterly ungraceful.
I have no problem with Guiding being all-female BUT it doesn't have to be so .... feeble. There is no earthly reason why they can't do all the camping, outdoors, risk-taking stuff that the Scouts do and which were the absolute foundation of Guiding (girls turnikng up at Scout jamborees wanting to join in). You can be all-female but still have a much less tame portfolio of activities.