Most GG acommodation is single sex provision. There is not the dorm space or washing facilities to separate by sex/ gender. I was a Leader before having DCs (sons). I logistically can't bring them to most venues within a 50 mile radius because there is not the provision to abide by the GG rules applying to boys. Yet if my long haired DS said "I identify as a girl" those rules to protect the girls and him go out of the window and he can be a full member 
Organising a pack holiday is a massive job. It has to be affordable. If it is too far for parents to transport, hiring mini-busses significantly adds to costs. It needs to be near appropriate activities. It has to be approved to GG standards. There are few venues that are practical to give the members privacy to their hearts desire.
On a larger camp, you have to submit your numbers then are given a tight pitch to arrange your sleeping and mess tents in. It might be a very awkward area (steep slopes, trees) and you are restricted to what you actually own. You're not free to just add some extra tents in because certain combinations of members don't want to sleep together.
Safeguarding for the very large camps is a massive logistical nightmare when there are thousands of teenage Guides/ Rangers, Scouts/ Explorers present. With those camps it is transparent that it is mixed sex for members and parents to make their choices.
I've recently attended Safe Space training. The comfort and feelings of the members are something we need to consider, rightly so. So why do the rights of transboys usurp several other areas of GG policy? Logically, it makes more sense to keep to single sex not gender and to support girls with doubts about their gender as long as they feel happy to retain membership, not to push them away in favour of the opposite sex who feel feminine.
I haven't spoken up within the organisation because there's enough to do to keep units running and more than enough shitty local politics interfering anyway. If leaders of active units stop organising residentials or quit or are evicted, then all the girls will miss out.