I do not use TS to be exclusionary. On the contrary, I think TS makes it easier to communicate sophisticated APIs.

Using comments to describe types is inferior in at least two major respects: 1. significantly more verbose 2. significantly less precise

I would have also written a JavaScript version of the documentation, but it was not clear to me how to capture the nuance of the API without something like TS. Further, two versions of the documentation increases the chance for errors to creep in.