Nudity is not strictly porn, but not all nudity is strictly harmless. Platforms like these are for clickbait and attention whoring, and there’s no better way to get attention on the internet than sexual content (especially on a website mainly used by kids/teens).
And it’s basically universally accepted that porn is harmful to children. We all watched some of it when we were young, but most people had circumstances that limited their exposure or access to it. A modern mainstream addiction machine like Twitch serving softcore porn to children under the guise of “artistic nudity” is going to fuck people up. That’s not even mentioning the “cam whore” aspect to it, which does frequently fuck up the lives of fully grown adults.
What sites are parents supposed to allow their kids to access if rules like this start slipping in? Short of invasive AI scanning, it’s not possible to monitor every single thing your child watches on a site at all times.