The difference would be that you still can call the function without await.

So this would be possible:

    async function f1() {
        f2();
    }

    function f2() {
        await fetch('something');
        ...
    }

Instead of having to async each and every function and await each and every function call:

    async function f1() {
        await f2();
    }

    async function f2() {
        await fetch('something');
        ...
    }

Which is what TFA complains about and what indeed is a pain in the ass.