The good engine doesn't know and doesn't care how much power the other engine is producing. When the other engine Fadec fails, it stops communicating with you and it stops communicating with the good engine. That's why you get a 'DEGRADE' caption on the good engine.
It makes no difference to the good engine whether the failed engine is producing 10%Tq or 100% TQ, it will make a difference to the gearbox though!
TeeS