Mecanim transition limitation/bug

I discovered a limitation with mecanim transitions that seems not to be documented. Typically transitions can be ordered within a state by dragging them up or down, however, it seems that transitions to other sub-statemachines are treated differently. If I drag one of these transitions to the bottom and run the game, Unity seems to automatically force it to the top where it takes priority over other transitions that are internal to the current sub-statemachine. Is there any explanation for why this happens? Is it a bug within mecanim? There seems to be a serious lack of documentation for mecanim transitions in general outside the manual which is incredibly low on details. The priority of transitions and the fact that they can be ordered also doesn't seem to be documented anywhere, I had to discover this on my own. Any help here would be greatly appreciated, as because of this issue I have to have all states on the same level and can't make use of sub-statemachines at all.