A quick follow up from me.
You can still repot IF it isn’t too hot. You keep the tree in the shadow for two weeks after. You do not make heavy root pruning. Only lift the tree and keep as many roots as possible. You know the tree is healthy.
No guarantees. This much depends on if you know the limits. Else, better wait until spring and give the tree time to strengthen up and grow. Give a good feed the full growing season.
If the soil drains well, there is no reason to repot this season. Only if there is a health problem, and it looks very healthy growth. So just keep it in the present pot for now if this is the case, and repot spring 2022.
I think it is an excellent material and viewed from the front is has this old look, so why not keep it that way. Stephenandra deadwood rots easily as Potentillas. They also often only shows thick trunks with several thinner trunks fused together. If you can keep them together I think you should.
The backside dead stump may be rotting away, but still, it is at the backside. I think this is a case where patience will pay off. Good luck with a very good material.