No, there are several formal MD/MS programs, and they work like MD/PhD where you just apply through the med school. As far as I know, there are no formal MD/MS programs that require you to take the GRE. CCLCM certainly doesn't require it. Even informal MD/MS programs probably won't make you take the GRE because you can just submit your MCAT score. That is what my state U's med school does.