This was a question comes from a Ward member that could not understand why it had to be done in a certain order.
I can't find anything official in the Help Center, but as I understand it based on past information provided from FamilySearch personnel, it mainly has to do with processing load during the merge. If the profile being merged in has a lot of data on it, that can crash the merge process. So the program occasionally has to force a particular order so the merge will be successful. In addition, one presentation in the past mentioned that the program does make at least some effort to have the profile with the longest Change Log to be the surviving profile.
One thing I can state definitely, is that it has nothing to do with particular ID numbers or with the Ordinances page. You will occasionally hear rumors that it does, but it does not.
Thanks so much for the information.