Sorry but the FAA isn't touting "safety" as the main reason for this NPRM. They view Remote ID as a necessary foundation for a new traffic management system - UTM (Unmanned Traffic Management).

Manned aircraft have always depended on "see and avoid" to prevent collisions when flying VFR. But drones can't "see", and there are too many of them, they fly too low, and are too hard for ATC to "see" to be separated by the current ATM system. The theory is that UTM will allow drones to "detect and avoid" each other because each drone will provide position and altitude information to UTM in real-time.

"Safety" in the FAA's mind is fundamentally about keeping drones below full-scale traffic. That's the reason for the 400 foot limit -- which has nothing to do with this NPRM.