Reason Child Porn became cheese pizza on 4chan is because of words filters that banned you automatically if you used the words Child Porn/Pron, a loop hole was used as pictures of Cheese Pizza, usually followed by a Pedobear meme and Chris Hanson and usually a Captain Picard would appear to say hello.

Childporn Being Cheese Pizza was/is a meme on 4chan. That being said, it still had DIRECT correlation to Child Porn A LOT of times.

https://voat.co/v/pizzagate/1621639 (related)

only thing that has been verified, as far as I'm aware, is "cheese pizza" = child porn

https://wikileaks.org/wiki/FBI_pedophile_symbols I've been to a site from Mexico that had it as well. I don't have a link for that though.