What about founders - they don’t just get stuck and give up on random technical things. There are many incompetent people who will sit around and twiddle their thumbs if nobody is actively communicating with them.

Wouldn't you go to experts outside of your companies? I may go to the company who makes the product for support or to a popular forum and ask a question.. none of this needs to be sync vs async

Exactly - what I mean by incompetent engineers is they will get “blocked” and then wait for someone else on the team to eventually find out and rescue them. Synchronous communication helps for these types of people. For engineers who can more independently work, and figure things out on their own (such as reaching out to experts if needed), asynchronous works fine in most situations.