I mean, technically he didn’t shut the door on the fight. He says he’d still be up for it if Elon ever gets serious, but he just isn’t going to waste any more time on it. Zuckerberg just doesn’t want a protracted will-they/won’t-they which is Elon’s bread and butter. Elon is the “master” of promising things and then never delivering, but never admitting it won’t happen either.