Did you have to do much to the file after "compiling" it in GM4Mac, or was it just a matter of submitting to Apple?
Apple sets some standards that you have to follow, so it's more than just 'compiling' the app: you need to take care of modifying the source code here and there to make sure the game meets those standards.
You may notice that YPWMI Lite behaves more like a Mac app, and less like a GM game (for example, it doesn't write its save file to the directory it's in). Little things like that are required by Apple.
After these are done, you have to modify a few parameters in the .app bundle (nothing too complicated), and submit.
All in all, it's a 'anyone can do it' process, if you actually know how the Mac platform works.