Apple just sues you, if they suspect, and the court will find out.

No, Apple rejects your app from the App Store until you can prove it's provenance.

OK. So it's even easier for Apple.

This is addressed in the original post. As of now, projects that were made other the the approved ones would have obvious file layouts characteristics.

Theoretically, you could make it hard to tell the difference, but in practice its pretty easy to tell machine generated from human written code.

You don't submit your source code to Apple as part of approval.

Yet! Wait for it serfs, wait for it!