I had a colleague who used to have very long pauses, but only after saying a few words very quickly first in a way that ensured he held the conversational baton. So he would say something like "I don't agree because..." followed by a 15 second pause before continuing the sentence.

Pretty sure it was not intentional, it was just what he had converged on as his optimal conversational strategy, but it was incredibly frustrating for others. Partly just the endless pause, but also I think (after reading this article) that everyone is busily optimizing a response in real time while he talks, but when he stops talking mid sentence, suddenly the algorithm has no more input to process yet still knows there will be more coming at some point soon, so cannot complete and also cannot swap out, so instead goes into an uncomfortable spin wait state that gets quite exhausting after a while.

His issue isn't non-blocking IO. Processing is preventing his single threaded event loop from doing anything else.