That'd only work if legal sex acts were the worst thing a kid could find online. As someone who went spelunking online as a kid. I assure you theyre not.
And the Roblox issue is hardly that of exposure to normal human biology.
That said this stuff should be up to parents, and instead of verification requirements, we should have parental control requirements (as in, the tools for it should exist).
On a lot of devices, I couldn't make them safe to hand to a kid without coding the tools myself.