Can a MWBC ever be on 2 breakers?
Yes, it was allowed to have MWBC on separate breakers. My house was built in 1981 and I had my refrig and two outlets on one MWBC and my dishwasher and disposal on another. They were not handle tied and not even next to each other in the panel but they were on different phases so the neutral wouldn't be overloaded. The whole subdivision was built like that and many panels that I've been in have had them wired the same way.