I am not being pedantic, there's critical fundamental conceptual difference that has real implications for how people write and reason about code.

There's performance reasoning, different level of guarantees, and entirely different programming model.

When someone hears "JS has built-in immutability features", they might think, "great, why do I even need to look at Haskell, Elixir, Clojure, if I have all the FP features I need right here?". Conflating these concepts helps no one - it's like saying: "wearing a raincoat means you're waterproof". Okay, you're technically not 100% wrong, but it's so misleading that it becomes effectively wrong for anyone trying to understand the actual concept.