On my test device, there are 15 calendars, some are duplicates (via being linked through different google accounts on the same device), and some are not duplicates.
Let X be the events returned from the first calendar. When executing the "Ti.Calendar.Calendar.getEventsBetweenDates" method on all calendars, they all return X. This is problematic, because we then cannot differentiate between which Calendars from which data is being pulled. A use cannot exclude certain calendars from being consumed by the application, which is a major issue.
NOTE: On iOS, this exact same scenario and code results in the proper data being returned from the specific Calendars.