Anyway, I found this gem on Apple's website:
"The Mastered for iTunes droplet is a simple, standalone
drag-and-drop tool that automates the creation of iTunes Plus format masters, allowing for a preview of songs using the same world-class technology used to encode the entire catalog for the iTunes Library."
In other words, it's just Apple's AAC encoder, and all it will do is make a 256k AAC file that throws most of the audio data away and makes an inferior copy of the original.
AAC is made technically obsolete by Opus, which is a royalty free lossy codec mandated by the WebRTC standard and fully supported on Android. In large public listening tests, it beat Apple AAC on nearly every track.