Parents have the ability to filter content when it comes to kids browsing their streaming services, but they have no control when it comes to the catalog. There should be some way for a parent to login to their account, and set filters for the linked children accounts. Filtered settings should have some way to be verified for plugins and other 3rd party add-ons. Technically, this could be circumvented by not logging in and browsing the catalog, if the catalog is open to the public. But there should be some mechanism in place to be able to do this if needed.
Another approach, or option for more sensitive or age appropriate materials might be to have an option in settings if a library wants to require a login to see those types of materials. If some materials are left out because of this setting, a banner could appear at the top of the results stating that a login is required to see the age sensitive materials.