There absolutely is a difference between inefficient and efficient communication, and you're right to highlight it. There is no gap between efficient and pleasant communication, though, and attacking pleasantry as if its sin is inefficiency is pretty messed up.

Like you say, that exchange is no less pleasant, and of course way more efficient, if it's one message with better information density. That takes some coaching, but the answer (and to be clear I don't think you're advocating for it) absolutely isn't "be a grouchy turd in the name of efficiency".

(And arguably that should then be an email, but most folks have forgotten that email exists, so, yeah.)