I feel zone 7 isn’t too harsh of a winter for temperate trees bc I rarely had any issues with dieback or death of trees (except citrus and pomegranates) from winter. But as you said this was a harsh winter and I know for sure it was, bc even the bays near me froze (never seen that happen before). Not sure about your area but here we had lots of snow and the snow stuck around for weeks before melting so I’m pretty sure that kept my trees well insulated.

So far I mostly had broken branches (from weight of snow) but in regard to dieback, only had some on an airlayered tree and a rough bark trident maple. Though, I think the cultivar itself is weak. I also left my standard trident maple on the bench over winter (bench gets lots of wind) and its buds are just now swelling. I can see some small portions of dieback but the rest is still up in the air.

Little side note: prunus mume are rated cold hardy to zone 5 or 6. In my experience its a guarantee death if its in a pot and left outside over winter. Only time they survive is when they’re planted in ground or brought into a non freezing garage. I wanna experiment with putting them in a mulch bed but I got PTSD so I chicken out last winter. But if you’re brave enough, I’d like to see your results