Which is why I put (facetiously) in my original comment. I'm perfectly aware that iceberg is really lettuce, and what I'm doing is making a "no true Scotsman" argument. It's all for fun. If I was being serious, I would define a new category, let's call it "tasty lettuce", which is a subset of lettuce and which iceberg should not be included in IMHO. But it's more fun to say something obviously incorrect but which conveys my meaning in ordinary conversation.