I understand your argument, that a court (in a democratic country with a rule of law) would expect that the investigators extract the original image from the ac

I understand your argument, that a court (in a democratic country with a rule of law) would expect that the investigators extract the original image from the accused's phone with the appropriate chain of custody of the evidence. However, that does not mean that while this investigation is under way, the accused is now go about their business. For CP, or other crimes of violence, that makes sense. But if laws are passed against peaceful protest, then that means someone could be held in detention while those photos are investigated. An anonymous photo now is trackable.