[yesco]

That's a strange example. An unauthenticated server on a LAN wouldn't be exposed to the Internet any more than a network using NAT would be. You would need to explicitly configure your routers firewall to expose a local node, the same way you would need to explicitly configure port forwarding with a NAT based network.

I've see some argue that a hypothetically buggy router would somehow be less likely to fail if NAT was used but really, that could be equally said about bad port formatting defaults, which have in fact happened. Complexity is what increases the likelihood of bugs at the end of the day.

NAT is just an addressing hack, a weirdly complex way of indirectly routing to local addresses. It only influences what is written on the envelope, not how that envelope is processed at the post office.