Tries to make massive judgemental claims, doesn't account for basics.

How about relative social position of the 2 people to begin with, where is that taken into account?

CEO talking to a junior employee who do you think decides when the conversation ends and how long it's going to be?

Entrepreneur pitching to a hotshot VC at a packed conference. Who decides when the conversation ends?

Context, power dynamic and bunch of other things determine how long the conversation goes on.

Keeping a conversation on or not is a social signal of interest - it means I am ready to give you my time (or not) - which itself is communication.

There is more nuance than asking 2 parties if the conversation ended at the right time and then proclaiming, "People don't know when to stop talking".