It is true. NAT only changes the source address used for outbound connections, it doesn't deny inbound ones.
You don't need to take that on faith either -- you can just test it.
You don't need to take that on faith either -- you can just test it.
How do you want to go about doing this? Although, 100% of the time people have asked me to do this they chicken out at actually doing it, so I suppose you will too. You might prefer to test with some network namespaces instead.