A picture or two of the embedded wire would be helpful.
Here is a page on that marker stone, it was erected in 1925. https://www.hmdb.org/m.asp?m=31193
That location looks too cramped up against the wall for the size of tree that it will become. Though you are certainly right the roots would not...
Pictures, both detailed and showing the overall plant, will help give a diagnosis.
Would this damage be considered partial graft failure?
The temperatures in vitog’s post look correct for November 11th, they must have just mistyped....
Our H. macrophylla our doing fine but the rhododendrons were hit hard. One in an exposed location lost all buds (as it had last year), I think...
Amelanchier alnifolia, Western Serviceberry is one of a handful of common names.
I strongly believe it would be part of the original planting of the park which would have been in 1985 +/- 1 year. Right at 40 years old as you...