“Many Lubavitcher Rabbonim wear a traditional Rabbonishe uphat even though the Lubavitcher Rebbe himself did not, and rather wore the same downhat as the vast majority of his Chasidim?”
Yes. The Rebbe wasn’t a “Rov”, he was the Rebbe. Besides, the Rebbe never wore Rabbonishe clothing, before becoming Rebbe he wore a simple hat and jacket.