The differences from doing it in iTunes on Mac is that 1) dragging files to iTunes changes the cursor so that it says "Link" while dragging and nothing happens, and that 2) I get an error message saying that it's not a valid app.
Now, building using the Ad Hoc profile results in an .app. There is a procedure described involving XCode where you open an archive and create an .ipa. Doing this allows it to be associated with iTunes in Windows, and double-clicking it is what showed the above error message.
Now, if I create an .ipa normally, I have to Show Package Contents, find the .app file, create a folder called Payload, put the .app there and zip it and rename it to .ipa.
But this .app file coming out from Corona looks different. There's no Products folder containing an .app, it just looks and acts like a straight zip archive of the development folder with all the files in it.
iTunes seems to have accepted the .mobileprovision, although no message appears verifying that. So I'm at the very last step where I install the app, everything up to this step checks out.
So. What's the trick?