Modular Frameworks and Build Libraries for Distribution incompatible?

TLDR; Why does Define Module not generate swiftinterface files?

This is a question that came out of my previous question, and maybe is more direct. That question is XCFramework with Static Framework Dependencies

What I am trying to do is build an XCFramework which I would like to be available for iOS and iOS Simulator. As soon as I turn on Defines Module and Build Libraries for Distribution the swiftinterface files are no longer generated. If I don't define a module then the files are generated. It archives and I can create a the XCFramework just fine. However when I go to import the sub framework that defines a module, it can not import the file. For a simple example of the issue I created a GitHub project.

If it Is not allowed it would be good to have an error or warning, but really kind of need this capability. Most third party libraries define a module, and I want to enable portability for my library.