The 3rd stage of the annual John Van Caneghem Tournament (2007).

Why do you think they might have mistakenly implemented it?
After all, the ballista is a ranged unit... it's been tested... archers affect it... And all ranged units have a shots parameter, and their number is always limited.
Otherwise, the cart would lose its purpose.

Here, the question is interesting, and VDV drew attention to this – the ballista is more related to equipment (cart, ballista, tent) than to ranged units. The tent has infinite healing, the cart provides infinite shots for ranged units, so it is logical to assume that the ballista has infinite ammunition because it is equipment, just like the cart or tent, and not a ranged unit. Therefore, it is questionable to assume that one piece of equipment depends on another, i.e., that the ballista will only have infinite ammunition if the cart is present. Then they would have made it so that the tent's healing is also infinite ONLY if the cart is present, right? By the way, the catapult also seems to have infinite shots?? I wonder where it will shoot if the battle drags on so long that all the walls and towers are destroyed, but the battle doesn't end? :) I hope I explained it.