That is very unlikely. I understand what you are saying but there is no training time between the two adventure parts for Lone Wolf to learn a new Discipline but if you like to play it this way, why not? Book 12 (end of Magnakai adventures) has only one part so even if you do this for book 5 you can't for book 12 or even 20. I'm not sure why the book is split into two like you say, perhaps it was an experiment of Joe's that didn't get repeated, perhaps he split it in two to help him write it and never got around to changing it.
Looking at the New Order Books (21+) there will be 11 adventures, with four initial GM Disciplines and only 15 needed to become a Supreme Master; it looks as if the final book will give you the opportunity to play as a Supreme Master, albeit with one discipline missing.