At the time that change was proposed, the specification was saying that browsers could optionally return, with some examples, but those are never meant to be ex

At the time that change was proposed, the specification was saying that browsers could optionally return, with some examples, but those are never meant to be exhaustive lists. If it's legal to do so, then your code needs to be ready for it. Relying on a browser's specific version behavior is brittle. And no, not all browsers currently do, all the browsers you've used in some specific scenarios behaved the way you thought, but there were already ways for it to fail before. As nice as it is, MDN and all the other websites are just paraphrasing what is in the specification, and sometimes omitting crucial information. Yes, Javascript and web technologies are accessible and can seem simple, but the reality is a lot more nuanced than it is portrayed in most places.