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. GitHub - possen/HostApp: Demonstrate issue with swiftinterface files not generated with Defines Module on.

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.