France with >85% IPv6 adoption mostly made of grandmothers driving a motorcycles across the town manually delivering packets like in their youth.
"Collectively, our results show that NAT has indeed acted as the de facto firewall of the Internet, and the v4-to-v6 transition of residential networks is opening up new devices to attack."
But the best de facto firewall is a proper firewall.
The point of my original post is that the author's take is controversial because people are skeptical about whether networks ARE being secured when NAPT is not present.
They are right to be skeptical, in my opinion, because the rollout of IPv6 has been bungled over and over again. That is not a problem with IPv6, its a problem with the adoption of IPv6.