The Boy Scouts made the decision in 2017 to start admitting girls and in 2018 started carrying that out. I think their split with Mormons really hurt membership and this was a way to increase membership.

As others have said - long before that, it was often the case that siblings and mothers (as leaders) were involved in troop activities anyway.

And yes, this story has nothing to do with Girl Scouts because as you say, they are an entirely different org.