The existence and creation of cigarettes and adult nude magazines is fully legal, only their sale is illegal to kids. If kids try to illegally obtain those LEGAL items, it doesn't make the existence of those items illegal, just the act of sale to them.

Meanwhile, the existence/creation CSAM of actual people isn't legal, for anyone no matter the age.

Grok created those images.

And when the magazines get sold who is breaking the law and gets convicted it is not the children but the shop supplying the children.

So when Grok provides the illegal pictures then by the same logic it is Grok that is breaking the law.