I think the Metro pilot would have assumed an engine failure because of he yaw that would have resulted from the collision. the Cirrus hit him on the right side so the airplane would have yawed to the right so the pilot has naturally assumed that the yaw has been created by an engine failure. He would have focused on getting it on the ground rather than trying to analyze what the engine indications are showing him. He might have also been confused why he didn't much rudder to keep it straight. The Metro needs some serious effort to keep straight if you lose an engine so the absence of that effort on short final (look at the photo of it over the threshold) would have been confusing but so close to the ground you are not going to waste time wondering what just happened. I think he has done a good job.