I have about 10 saplings that I wintered outside this winter and they too have a lot more freeze damage than my standard obtusa, but they are pushing a lot of new growth. I plan to give them a bit more protection next winter. Unfortunately not a lot of care data for them.
I’m not so sure it is Winter protection.
All my trees go under my sunroom on the N side of the house in December
No direct Sun, no snow, no frost. Only water.
is there any chance yours could use more water? It is possible on my end.
Perhaps next year I will heel one into the ground exposed to snow and frost, IDK.
You‘re in a better situation to try this than I, having several.
I only have 2 in clay pots + 1 cutting that survived Winter stuck in a nursery can
with a fir tree I believe.