Hi jordan,
you are lucky today, as I am sitting around, waiting for a craftsman I called to repair a broken window glass. I just went into the basement, got the stator on the bench and took some snapshots,
http://ducwiz.minus.com/mOqLCAKPA/.
I always wondered about the detail you mentioned, too. My idea: it is basically a short circuit winding, mutually coupled with the charge coil. From my knowledge about electric current transformers I conclude this winding to be a low pass or smoothing filter against voltage spikes, which could damage the electronics inside the CDI transducer box.
I never had an opened Motoplat stator on hand, I always avoided the Motoplat CDI due to many reports of weak sparks or total failures. I only remember that the HV winding is grounded here, in contrast to the DUCATI item, where it is floating. That's why the no. of output wires differs, 4 or 5, respectively.
Edit:I found an interesting url in my bookmarks, but haven't read this page dealing with the DUCATI CDI in the Moto Morini bikes, due to the craftsman's arrival ...
http://www.motomoriniclub.nl/tech.html#Morini%20ignition%20systemHans