As a type 1 diabetic, I don't think this is very relevant for treating diabetes. The VX-880 trial already used stem cell derived islet cells (that's not the same stem cell therapy as the one described in the article), so the need for donor cells will go down. Those grown islet cells won't have rejection problems because they would be a match to the patient's body.

A cure for type 1 diabetes requires two big steps: First, cells have to be lab grown (already done in the VX-880 trial). Second, the faulty autoimmune reaction needs to be fixed, or the islet cells need to be encapsulated somehow. Otherwise, the immune system kills off those cells again. The approach described by this paper would not help, because those islet cells would be the patient's own already, so there would not be any "hybrid" immune system. It would not make sense. Also, procuring donor islet cells is difficult and wasteful - another reason why lab-growin islets instead is a much better approach.

However, this is of big interest for organ transplants. People with those have to take immunosuppressants, which are no joke.