Officially the RMH does a rack or stepping rack as some call it.
Here is a video of CCFs Shiloh(just happens to be brother to my boy,lol). He has a very even gait, if you turn up the sound you can hear the 1-2-3-4.
Here is a video of a UMH/Rocky show. In the video you can see two horses. The second, a black horse, is doing a horrible stepping pace, almost a straight pace. This is a pretty blatant example, but you can see how both feet on one side hit at almost the exact same time.
Your boy is still very young, as you said I think he just needs some time and maturity, and also muscle development to be able to hit a nice even gait. Something that you can do to strengthen his gaiting muscles, surprisingly enough, is walk walk walk. Other breeds are not so much this way but with the Rockys because their gait is basically a fast animated walk you can build muscle by walking. Try some hills, riding in tall grass, etc...