Okay but why does this matter? They're your ISP they also have your address, credit card number and a technician has been in your home and also supplied the router in the common case.

The theoretical vague problem here is being used to defend a status quo which has led to complete centralization of Internet traffic because of the difficulty of P2P connectivity due to NAT.

No device on my ipv6 vlans can establish P2P tunnels outside with random clients.

Firewalls and good old monetisation prevented your p2p connectivity utopia, not nat.