When I’m composing a message, under the “Parent” section most parents have their Scout(s) listed underneath them, but not all. Mainly it’s new Webelos 2s who crossed over recently, but it’s not limited to just them. For example, my own son does not show up under me. We have granted him access to Scoutbook and I show up under him. Another family has the father showing two sons, only one of which is still registered with BSA, and the mother only shows one (the one who is registered).
I don’t think this a connections issue, because all the parents have full control by default and I’m a unit admin and Key 3. Some of the new Scouts have different last names as their parents, and it would be helpful for all Adult Leaders to have all Scouts listed under parents.