This is not quite correct.
The Java plugin adds the ability to declare dependencies on the implementation configuration, but not the api configuration. It does add the ability to properly consume other modules that have api dependencies though (it adds the apiElements configuration for this).
The Kotlin plugin itself is actually adding the api configuration that you can add dependencies to and it does set up a few additional items if the java-library plugin is applied. Will you notice the difference? Depending on what you are doing, maybe not.