Doesn't matter. They needed a CONSISTENT, CLEAR policy on children, that could be consistently enforced by security.
"No children under 16" is a clear, enforceable policy. Don't have ID showing you are over 16? You don't get in, unless you are very obviously an adult.
If I were running it, I would not want the admittance line slowed by arguments between parents and minimum-wage security guards over whether a particular child would be safe in the show. I would tell the moms "Sorry, that's the rule. No, I won't make an exception just for you. Bye."
You make a good point there, PapaBear.