A few thoughts:

• setTimeout et al aren't a bad way to introduce asynchronous programming; whether they need to be introduced in depth to introduce the concept I'm less sure
• the title "cooperative async JS" is weird; I know it's not one that I would have used, nor one that evokes anything related to setTimeout et al
• while there are a number of use cases where requestAnimationFrame is a better replacement to setInterval, that's not a general statement (e.g. a timer); in particular, I don't think we should keep the qualification in the article of the former being a modern version of the latter; conversely, it would be useful if the introduction of the section on setInterval had a link to requestAnimationFrame explaining when it is a better alternative

All in all, my thinking would be:

• consider whether setTimeout can be used as a gentle on-ramp for asynchronous programming (I know I've used it in courses I gave on this in the past), but not necessarily doing the deep dive on its syntax and semantics in the async section
• move the deep dive and the description of the other two in client-side APIs (for lack of a better subcategorization)
• clean up the relationship between setInterval and requestAnimationFrame

(as an aside, clearTimeout could be used as on-ramp or in a similar context to AbortController - not sure if that is or even should be covered in this learning area)