Comment by Dagger2

You can't get a packet from a random store wifi network to your home network when your home network is using 192.168.* (barring something like routing headers, which most routers wouldn't process). You said that yourself in the first part of your post, and I don't think I ever argued otherwise.

> Symmetric NAT 100% stops inbound unsolicited connections to the public IP

No, it doesn't. If it did it wouldn't be possible for routers to accidentally make their web admin or UPnP interfaces available to the Internet.

It doesn't stop connections to your router, and it doesn't stop connections through your router either. It just plain doesn't stop connections, which is why it protects you from 0% of attackers.