I think there are two key differences between Scouts and Guides on this right now. Scouts recognise that there are two sexes and Guides don't. Scouts have long needed to figure out how to accommodate those two sexes and Guides haven't.
However, both are similar in that individual leaders are the ones making the granular decisions you're thinking about e.g. whether Blue should share with Freya or Fred. In either organisation, it's possible that a captured leader could create a mixed-sex sleeping arrangement without telling anyone. Or that a captured parent could put a child into a group without declaring their true sex.
I'm a Scout leader for ages 10-17 and, in my county, I think it's extremely unlikely to be happening. Safeguarding policies keep adults (age 18+) and children (age 17 or younger) strictly separate. Anyone in a position of power (e.g. a young leader working with younger kids, like a 16 year old working with Scouts aged 10-14) must have separate accommodation from the kids they're working with.
As I said up-thread, Scouting is a welcoming home to young people who don't fit into other places. Some of these young people have blue hair and pronoun badges, and rather rigid thinking about rules: I get the impression that they take their Scouting and safeguarding responsibilities seriously - and that they are keeping themselves and others safe by maintaining sex-separated sleeping arrangements for themselves. I can't be sure - noone can, while so many people are still confused the difference between sex and gender - but that's what I think is happening.