Assumptions like that can be done endlessly and you will never get 100% satisfaction but vanilla JS is the title and the main target here IMO.
You do not start learning JS by doing some heavy dutty React+Redux stuff.
Same goes here, it's a "get basics" lesson.
I agree that everyone should use Typescript but knowing what Typescript adds to Javascript doesn't help you with anything. You have to know Javascript first; because that's what the bulk of your code is. Typescript merely adds some annotations and all of its syntax strictly deals with types.
Your statement kind of sounds like "don't learn C, learn how to run gcc from the command line". Important but orthogonal.
I think people miss the point that it is just a compilation check, but the runtime is still completely dynamic. If you are writing typescript that interacts with anything else in the world the types make no guarantees at runtime so it is important to know how Vanilla JS would behave in that circumstance.
I might have plans to add a TypeScript chapter towards the end
Nope, it doesn't
No because then you'd be writing TypeScript which is not Javascript anymore than CoffeeScript is.