If the device was “factory reset”, it’s not really your device any more (as in, Apple no longer knows it’s your device). If “Find my…” is the system Apple uses

If the device was “factory reset”, it’s not really your device any more (as in, Apple no longer knows it’s your device). If “Find my…” is the system Apple uses to prevent devices from being used after theft, then they should just make it mandatory, or at least very difficult to opt out.