NAT does nothing? The NAT setup is the reason incoming connections don't reach devices on the LAN. I get that you can phrase this as NAT actually being the thing forwarding the packets, and on a home ipv4 router without NAT the incoming packets would just go nowhere, but everyone is talking about the realistic options of NAT vs device having own public IP addr.
I get that an ipv6 router can have a firewall with good defaults blocking incoming connections, emulating that aspect of a NAT.