I think the confusion stems from the fact that my mom's laptop with its 192.168.0.43/24 v4 address is not routable except via NAT, and people believe (rightly or wrongly) that that confers a degree of security.
e.g. symmetric NAT exists and often doesn't come with a stateful firewall. Just because the linux box with iptables is protecting your network uses NAT doesn't mean NAT is doing the heavy lifting here. I can see the OMG MY PRIVACY crew is out in force here apparently misunderstanding that NAT does not do that either. I mean, we can explain things to you, but we can't understand it for you.
I know that, and you know that, but squillions of people think that turning the UPnP setting off (if they even know what that is) is sufficient, which is why the myth persists.
And yes, everyone is aware that you could also do that with a stateful firewall. And no, none of us care about arguments of definition that attempt to frame NAT as technically being a firewall based on how it operates in practice. Being intentionally obtuse by refusing to acknowledge the obvious isn't going to convince anyone.
It's INCREDIBLY unlikely to find a case of that in the wild, but possible.
A common example of a host that might have such an address but lacks that sort of security is anything as the default route for inbound packets, E.G. like you'd want your _own_ router / firewall rather than the ISP's modem.