I'm a Scout Leader
Firstly, the session your child had tonight was probably the bit of the World Challenge badge about differing beliefs in gender, sex etc.
Secondly... camping. Yes, I agree, the "guidance" is open to interpretation. Especially since, Scouts don't insist on single sex sleeping arrangements (but in practice it happens most of the time). They do however insist on single sex changing spaces. The mixed sex sleeping arrangements refer to big groups in a hall, or outside in shelters etc... not that a singe boy and girl can share a 2 berth tent!
I've had a trans identifying Scout. They used the facilities of their sex not acquired gender.
The reality is teens (and younger) are identifying as Trans and it would be wrong (and illegal) to exclude them because of that., so we need to adapt to they are included and single sex boundaries are not overriden. We can't just pretend it doesn't happen.
(I would cancel an event rather than let one Scout dictate sleepinh and changing arrangements l. But in the meantime... I prefer to protect children by being in the organisation rather than just walking out based on a theoretical)