I'm really hoping they are pouring as much effort into training digital forensics to expose entire networks and sources when one node is caught.
As it stands, I can imagine Android or iOS being called to the dock for being originators of the images as they'll have to pass through an OS of some kind unencrypted at some point. Going after messaging services seems like law enforcement have given up policing and want some easy wins but are too toothless and unimaginative to go after the most culpable platforms, if you're going to start pointing fingers at the noncriminals.
They offer entire photography, editing and production suites, without the privacy guarantees of the messaging apps.
Google, MS and Apple should be first to offer help here. Or be called on to do so.