That question has remained unanswered.
I wonder how much Beta testing the Upgrader is getting. As not seen much feedback here on user experience and findings so far.
Probable explaination is that most users already have the latest version of ZorinOS (Z16.2) installed, so there is not much scope to test the Upgrader untill new Z17 version is released.
EDIT: I have now just seen this item: I can't update anything
EDIT2: I have just run Software Updater on Z15.3 Core. There were some updates available, including the Zorin Upgrader. "Upgrade Zorin OS" is now listed as menu item under Zorin>System Tools. So I guess Beta testing is done and devs have launched the first Production version of the Zorin OS Upgrader app.