There are a couple difficulties with this. For starters, in order to make lidar eye safe, it has to use incredibly short pulses of light. You're saying we need to take that single pulse and replace it with enough of them that it has a unique fingerprint - realistically it will have at least 5x the energy. Add in signal degradation and a safety buffer and you likely need at least 10x the energy to uniquely identify sensors. Suddenly the invisible lidar is visible and dangerous for regular use. Of course this only applies to the visible spectrum - Luminar is actually unique in using a 1500nm laser. In addition to the above, it just makes everything a lot more complicated and expensive when everybody is racing to make it cheaper.