look into how React Suspense hides asynchrony (by using fibers). its very commingled with nextjs but the original ideas of why react suspense doesnt use promises (sebmarkbage had a github issue about it) is very compelling
Compelling? It's freaking terrible, instead of pausing execution to be resumed when a promise is resolved they throw execution and when the promise is resolved the whole execution runs again, and potential throws again if it hits another promise, and so on. It's a hacked solution due to the use of a global to keep track of the rendering context to associate with hook calls, so it all needs to happen synchronously. If they had passed a context value along with props to the function components then they could have had async/await and generator components.