I have never seen any situation where this is not already necessary other than UPnP which already almost never works reliably. A publicly-addressable relay is already practically non-negotiable for anything over the internet.
Without NAT, it wouldn't be. That's the point.
uPnP works fine though? What was the problem you had with it?
loading story #47690381
loading story #47691585
IPv6 everywhere makes that not necessary, which is what the author is pushing for.