Military combatives, whatever the version, have two basic purposes; 1) help to instill a fighting spirit, and 2) give the military personnel tools when they cannot use their firearms or other weapons. They aren't designed to make an MMA competition fighter, so it's no surprise that the average soldier* isn't on par with the average MMA participant -- including serious hobbyists -- in the MMA arena. Just like I wouldn't expect the average MMA participant to handle Close Quarters Battle. Unarmed skills aren't the primary focus of most soldiers, because they generally don't expect to go hands on with the enemy.
The Marine Corps Martial Arts Program does use "belts"; it's a ranking system that indicates the amount of time and what training Marines have gone through within the program. And, like any ranking system, really has no meaning outside its own context.
Police Control Tactics (or Defensive Tactics) have a different purpose, because a police officer will likely go hands on many times more than a soldier. After all, at some point, the cuffs have to go on -- and that takes going hands on. They also work with different rules of engagement (in the US, the Constitution, 4th and 8th Amendments especially). So, once again, the average cop isn't going to excel in the MMA arena... nor is the average MMA fighter going to be able to effect the arrest of a subject as well. They might well successfully submit them -- but what do you do with the guy once you've got him in a crucifix or some other submission hold?
Note also that we're talking averages. I know cops who are MMA fighters, soldiers who train BJJ, etc. Oh, and a fair few cops who train in a various different martial arts, too.
*I know, Marines and Airmen and Sailors aren't soldier, but it's easier than writing all of 'em out or writing military personnel everytime