Intellij idea packages 3 moudules into one jar while I select 'copy to the ouput directory and link via manifest'

Here is my project. It contains 3 independent modules. And robin-app has reference to robin-springroot, and robin-springroot has reference to robin-springroot-plugin.

While packaging, I choose copy to the ouput directory and link via manifest, and I guess in the final output folder, I should see robin-app.jar, robin-springroot.jar, and robin-springroot-plugin.jar the three files. But I find that I only get robin-app.jar, and it contains all the classes in other modules. Why is it? Thanks.