As it has to be. Because there's no defense against the possession of it, you don't want a situation where a person under 18 can take pictures of him or herself, send it to an adult unsolicited, and then call the police and not suffer any consequences.
That doesn't make any sense and it's not how it works in a number of other countries. You could (for example) make it illegal to send these pictures instead.
People own their bodies. Taking pictures of yourself, if you're a child, isn't child porn any more than touching yourself is molestation/assault.
Children don't need to be hit with "strict liability".
A person trying to frame someone else of a serious crime commits a serious offense, yes.
But that's a logically separate concept from the production or possession of child pornography, which that person must not be regarded as committing if the images are of him or herself.
The idiotic law potentially victimizes victims. A perpetrator can threaten the child into denying the existence of the perpetrator, and into falsely admitting to having taken pictures him or herself. It's exactly like taking the victims of human trafficking and charging them with prostitution, because the existence and whereabouts of the traffickers couldn't be established.
Whoever came up with this nonsense was blinded by their Bible Belt morality into not seeing the unintended consequences.