Sure, and that's fine, but relying on it isn't, and it isn't a reason not to use IPv6 (if you want namespacing, there are tools for that outside hiding behind a single IPv4). Hence the advice is not to rely on NAT.

This is people talking past each other, and to be fair, saying "everyone" in my post made it unclear, I was being glib in response to "because that's not what people run IRL", when evidently people do, I've seen it happen.