Promises with single-fetch vs. defer

[kc0506]

I recently checked this video, and I am trying to achieve similar effect with single-fetch, since defer seems deprecated.

The docs suggest one can simply return the naked promise. However, this is not the case in this demo. The fetcher continues loading until the promise resolves, and the fallback of Suspense never show.

Did I miss something? What is the correct way to handle this? And if the fetcher (or useLoaderData) can only return promises when they resolved, what would be the benefits doing so?