11-21-2016 01:26 PM - edited 11-21-2016 01:30 PM
To paraphrase what I said somewhere else:
Most publishers actually specify the order to be based on alpha (author) then year and then usually title, which is what you are getting, and not in order of citation appearance. That is because in the bibliography itself, that is how they want them to be listed.
You could make this change in the citation sort order and let the bibliography be listed in Author, Year, Title and then the letters would be out of order there, if you prefer, but I didn't test that option.)