You're missing my point. All I'm saying that the evidence the burglar provides by turning himself in with the evidence is far stronger than that provided by mailing in a phone, which is a fact. If you send in a phone with child porn on it with a note that says "I stole Humbert Humbert's phone and it has naughty pictures on it, arrest him", and they search his place and don't immediately come up with anything, they're probably just going to drop the case, thinking the phone was out of Humbert's hands when the porn showed up on it.
Suggesting that the burglar should not have done what he did is silly, since A) this Australian criminal probably knows a fair bit more about Australian law than you do and B) turning yourself in for a crime you committed is, regardless of child porn, the right thing to do.