I think the point he's trying to make is that if you make a blocking system call, it blocks the thread that goroutine is scheduled within, but other goroutines

I think the point he's trying to make is that if you make a blocking system call, it blocks the thread that goroutine is scheduled within, but other goroutines will not be blocked by this and will continue to execute. This is not the case with many other (single-threaded) systems built exclusively around a god-loop that schedules coroutines. One coroutine making a blocking system call gums up the whole works.