Agree on the second point. It's possible the Reds' reliever would have given up the runs anyway.
On the first point, if Arroyo comes out, Reds would have (should have) double switched Frazier into the game anyway. So I don't see why the Reds inning should have been different.
Bottom line, if I knew Arroyo should have been out, the Reds should have known it.