I love JSDoc but it has the fatal flaw of being optional. It requires human discipline which, when your boss is breathing down your neck to get that feature out, you aren't gonna do. Same goes for robust tests etc. TS is self documenting even if it's less verbose you'll get more coverage overall in your system and maybe have some hope of being able to to back and write those JSDoc comments later. You also don't have to write as many tests as you can be somewhat assured of data integrity since you've defined a robust contract.

TypeScript annotations are also optional.

In my experience, TypeScript does not reduce the number of tests you need to write.

Well yes and no. Even if you don't add any type annotations you still get some implicit type safety. You have to opt out with an Any type of something to totally turn that off.

Our experience is different with tests.

The TypeScript engine in VS Code does the same type inference for standard JS, and automatically downloads d.ts typings for libraries you use to enhance it.