I just checked and it shows:
It doesn't say that in mine.
Additional Card Members do not have accounts with us but can use your Account subject to the terms of the Card Member Agreement, must be at least 13 years of age and never had a default account with American Express. You are responsible for the activity and use of your Account by Additional Card Members. You must pay for all charges they make.
I have been getting the pop up about the AU card for 18+ but when I click to the Add A User page - it references 13+.......
Hmm. My account has said that for awhile. Obviously Amex assumed I couldn’t delegate any responsibility lol