Parameters required by default when generating modules from JavaScript files

TypeScript Version: 4.1.2x

Search Terms:
transpile javascript optional parameters

Code

export default function example (hello, optionalParam={}) {
  console.log(hello);
}

export default function example(hello: any, optionalParam?: object): void;

The first parameter is now required. While there is syntax to make parameters optional as shown above, shouldn't all javascript parameters be optional unless specified by a JSDoc?

Ideally there would be some configuration for this to allow a "optional by default".

Expected behavior:
https://www.typescriptlang.org/docs/handbook/type-checking-javascript-files.html#function-parameters-are-optional-by-default

Actual behavior:
Parameters are not optional by default.

Playground Link:

Related Issues:

Start by reading the handbook section on JavaScript function parameters and reproduce the example with the TypeScript 4.1.2x behavior described here. Investigate how JavaScript files are checked and how optional parameters are configured; done means the documented optional-by-default behavior or an explicit configuration choice is consistently reflected in the reported types.