I think the point here is that all the TS tooling works with JSDoc without any friction. As long as you don't look into the file, from the tooling perspective, a .ts file and a .js file with proper JSDoc annotations are practically the same.

Except the js files can work in the browser as is.. not the ts one (fortunately I might add, I find ts syntax very loaded at times) Either one is superseding the other one, or they are simply distant cousins, but this is not interchangeable.

TS from JSDoc requires a generative pass to. This is a (expected) level of indirection. (unless some tooling does it automatically)