> I'm much more comfortable with threads

The example code shown in the first few minutes of the video is actually using regular OS threads for running the async code ;)

The whole thing is quite similar to the Zig allocator philosophy. Just like an application already picks a root allocator to pass down into libraries, it now also picks an IO implementation and passes it down. A library in turn doesn't care about how async is implemented by the IO system, it just calls into the IO implementation it got handed from the application.