the lucrative parts (screen, camera arrays) are serialized and will not work on phones other than the one they were built for

almost everything else is soldered onto the logic board and is futile to transfer

so i think that stolen iphones with activation lock are 100% paperweights.

But it lowers the incentive significantly regardless.

Thankfully Apple is working on that by pairing the parts to the motherboard and showing error messages if they don't match.