You can do that, Joey, but the problem is that when you export your iOS project to a movie you are rendering all the transitions, cuts, etc. that you make in iMovie for iOS, and then if you need to do more work with the movie on your Mac, you have to ultimately render it again. Each time you render a movie, you degrade the final quality since the mp4 compression codec used by iMovie is a "lossy" codec.
This is why we NEED the original functionality restored to the new versions of iMovie for iOS and iMovie for Mac. The old method allowed us to export and import the PROJECT with the original untouched video files, finish our editing, and render the project ONCE. Please Apple, restore this functionality to iMovie.
As I have previously suggested, there is nothing in the new versions of iMovie on either platform that comes close to being as valuable as the ability in the old versions to export from iOS and import the projects into iMovie for Mac. This is why I have downgraded my workflow and still use the old versions of both apps. If Apple ever restores this function, then I will happily start using their new versions of both programs.