Oh good, I was wondering when the trolling would start

Unless/until the airline sets a policy that no lap children are allowed on a paid F ticket, you're just wrong.

At present I can buy an F ticket for a child or an F ticket with a lap child on UA so children clearly belong in F if their parents choose to pay for it.

And even if mom and child were on an award/upgrade, the fundamental fact that UA will sell F to a parent with a child means children are allowed.