The spirit of the law is that it's limited resource that was specifically designed and sized for small children and perhaps a limited number of their caregivers. That was specific in the Hollywood, FL ordinance (“maximize play area equipment available for children and minors for whom the city’s play equipment and play areas are specifically designed.”). It's not like these rules are unique. Here's a playground in London named after Princess Diana, with a more impressive looking ship than the one I visited:
Does look rather fun though. However, it sounds like they're able to enforce this at a gate.
I'm used to these kinds of restrictions. We used to have a membership at the Children's Fairyland park owned and operated by the City of Oakland. It's been brought up as one of the possible inspirations for
Disneyland. Walt Disney hired their director to work at Disneyland. Their policy is no child without an adult and no adult without a child. There are quite a few children's museums where the policy is similar. One I found has a policy that a photo ID must be left for an unaccompanied adult. Another allows unaccompanied adults to tour the facility, but only with an employee.