Whales ARE fish
Whales ARE fish
I had a whole deleted other paragraph in the OP about how everyday language isn’t beholden to strict scientific nomenclature, in which I mention tomatoes specifically. A chef probably doesn’t care about the exact botanical definition of “fruit”, and is more concerned that tomatoes pair well with savory foods like other vegetables do, so forcing the distinction in this case would only confuse things.
I know I’m also undercutting my own joke, but calling whales (and humans) “fish” in the cladistic sense, while true, is also not very helpful.