The law must recognize the right to self-determinism and bodily autonomy, and you can't inherently be both the victim and the abuser. There is no one size fits all law, and many governments are trying to act like they have one.
Do you have a concrete example of this happening? Every time I have heard of a minor being persecuted for possession or distribution is when one person sent an image of themselves to another person and then that other person further distributed it to other people without their consent, which to be clear is wrong.
https://www.aclu.org/news/juvenile-justice/minnesota-prosecu...
This is one such case, but hardly unique.
No not really, sharing sexual images to others that were shared to you directly by a person should be (and in some countries is) a crime. The boy in the linked case should be the one charged with the distribution of child pornography, or something akin to revenge porn since they are both minors.
It is probably very hard to carve out these exceptions for minors sexting, but we already have (in some countries) consent laws that factor in relationships between minors. I don't see why this would be different
Generally the process isn't worth it unless they think they have a near certain chance of winning against the child.
I do agree, however, that in bird culture, sharing nudes that were sent to you is considered a dick move.