The dominance thing would make sense, based upon what I have seen at playtime.
During playtime, dominance humping is an issue. I always break that up because I know it could lead to a fight. The chin with long whiskers tries to hump the chin with short whiskers several times during playtime. The chin being humped barks and tries to run away; he doesn't just sit there and take it. I can tell when the humping will occur because the dominant chin runs up behind the passive chin. The passive chin starts to make this kind of quiet "don't hurt me" squeal noise. Then the humping may or may not occur. It is nice to have that warning noise so I know when to be prepared.
Occasionally the chin with short whiskers tries to hump the other, but not nearly as often.
In the cage, the chin with long whiskers tends to sleep hunched over the chin with short whiskers. However, the chin with short whiskers enjoys taking any wood the chin with long whiskers is chewing on.