NAT in its customary usage is a bit of a historical accident that as a side effect happens to make it basically impossible for non-technical people to expose their devices.
In the post I was replying to, the hosts were already unreachable (or... mostly unreachable, not completely unreachable) before NAT was even in the picture.
If I want all the computer on my network to have Internet access, I have two options: Each gets a publicly routable IP, which results in all computers being exposed to incoming connections unless I have a firewall, or I get a single IP which gets assigned to my router, use NAT, and all my devices are no longer exposed to incoming connections unless I go out of my way to configure port forwarding on the router.
So when I talk about the "side effect of using NAT", I really mean "side effect of using NAT instead of assigning public IPs to each computer on my network".
Does that help clear things up?