If I understand correctly, this same problem pre-existed in the Yahoo group...the transfer simply brought it to light. In that sense, it's no different from people who landed on "no email" delivery only to later start bouncing, complaining, etc....
Depending on how you look at it, it's an annoying inconvenience, or an opportunity to perform housecleaning that perhaps should have been done a long time ago. Either way, it doesn't strike me as a serious shortcoming of the existing GIO platform.
Bruce?
Bruce