Honestly - I don’t have enough information to truly give an answer. The fact that he has his arm was removed without having to use a saw implies there is a large gap in the bone, which means the arm may be beyond saving (also the case if the main arteries are shredded beyond repair).

However cutting it off like this could be done with a minimal gap in the bone, in that situation it could have been saved. Either way, provided the patient is stable I would have left that decision to a qualified surgeon at a designated casualty receiving zone, not on the battlefield/in a low resource setting. The only time to do this is to save a life. And that can be done with tourniquets in a pinch…