The point is very clear to the rest of us. You inserted the word "full" where the author was not talking about full agency. It's hard to believe that you don't follow.
We are arguing over how much agency children should have. The article argues they should have more, the comment you originally responded to said practically definitionally we limit the agency of children. The obvious implied point is that it's not unreasonable to think their phone use may be part of the agency that they are denied, and that would not be a departure from how children are treated.
