Interesting. Should probably note that I was the commander of the army so I wasn't experiencing the random command bug, but it makes sense if the AI was the commander and treating it like a regular battle.
Earlier this evening I had my army in a Castle to defend against an incoming army. Both armies treated it as a normal battle. My infantry and archers were running into the walls inside the castle trying to get outside. My Cavalry was climbing the walls (a handful managed to yeet themselves off...