I've mentioned this before, but if you haven't merged your accounts yet, why do it now? I guess I assumed that people that distrusted Marriott IT so much that they were hesitant to merge accounts had actually made the decision to permanently abandon one of their accounts at this point.
For example, there seems to be a lot of former SPG people posting here that didn't have much Marriott activity. Since there were glitches with some mergers with a lot of SPG activity, people might choose to just not merge, let the SPG convert to Marriott Bonvoy, and just never use the old Marriott Rewards account again.