It's basically, "I want context switches syntactically explicit in my code. If they aren't, reasoning about it is exponentially harder."
And I think that's pretty clearly a strawman. Everything the author claims about threaded code is true of any re-entrant code, multi-threaded or not. If your function inadvertently calls a function which calls the original function recursively, you have the exact same problem.
But, guess what, that just doesn't happen that often. Most code isn't re-entrant. Most state isn't shared.
For code that is concurrent and does interact in interesting ways, you are going to have to reason about it carefully. Smearing "yield from" all over your code doesn't solve.
In practice, you'll end up with so many "yield from" lines in your code that you're right back to "well, I guess I could context switch just about anywhere", which is the problem you were trying to avoid in the first place.