Back when mandatory seatbelt laws were debated, people used to concoct scenarios where a rider/driver is saved because they're not wearing a seatbelt (they were "thrown clear").

This reminds me of that. Your "safety in numbers" and "cars pass closer to helmeted cyclists" is a desperate attempt to avoid a simple fact:

if a head hits the pavement without a helmet, it gets injured.

Of course you can invent other scenarios, but only by ignoring that one.