I did the same thing with my parents, mostly because they’d just say “quarter after” but would never say any number. If you made a word cloud of everything I’ve ever said in my life, “after what” would be gigantic in the center with every other word tiny around the edges.
The point isn’t age verification, the point is being able to say “look, we have an age verification step, we’re not liable”
You don’t need a separate account to play Leagues or any other temporary game modes. You are correct however that you do need to pay a separate membership for each character unless you’re okay with that character only being able to do F2P activities.