Are they doing anything with the on-device "Hey, this image someone texted you may contain nudity, are you sure you want to see it?" sort of filters with what's displayed in apps, or is this a parental control option?
Mostly, they're in the App Store with age ratings of 17+, so parental controls will block them out. No idea how that system interacts with third party app stores, either -- but if it doesn't work there, that was very much Apple's implementation-choice.