Tears, maybe you're thinking of when an attack was initiated with more than 1/3 troops, but the defenders then reinforced such that defense outnumbered offense by more than 3 to 1. In this case, there is a time slot scheduled, but there is still no autocalc, you actually play out the battle.
I don't think the no troop minimum is a problem. It might be, if dozens of tiny battles are clogging up the servers, but that's not really an issue yet. I actually wish there were more to be gained from small battles, since at the moment, strategus is extremely heavily inclined toward factions, and there is very little room for individuals, or small groups, to even RP banditry or something.