Optional types don't fix this. The problem here is not having default (or named) function arguments. With optionals, you still have to pass every arg explicitly.
Languages with both of these features like Python don't end up using the builder pattern or reinventing it like this author.
To solve this problem, a language have to disallow null/nil as a bottom type and provide nice syntax to initialize types with optional types.
[1]: https://geeklaunch.io/blog/make-invalid-states-unrepresentab...