Yes, if you are the GM you have more dice (if you want them) and can play A/A/A and pretty reliably win with some sort of compromise. But why do you want to settle for a compromise? Why not take sweet unspoiled victory?
Once one side either really needs their Goal, or can’t abide the other side’s Goal, they’re willing to play something other than A/A/A, because A/A/A is a recipe for not quite getting what you want.
And once one side isn’t playing A/A/A, the other side can do better by scripting well. Once you’ve won without losing any dispo, you’ll never worry about A/A/A. You may use it occasionally, but it’s not a problem.
“I am a predator. I want to eat food. If I get hurt too much trying to get THIS piece of food, I will not be able to catch other food in the future. (I may also become prey, myself, if I’m too hurt to run at full speed.)”
This is, basically how most animals hunt. Most animals have to juggle “I’m going to eat now vs. I’m going to be able to eat later.” Most predators are not going to want to lose 1/2 their disposition and get serious injury.
They came expecting mice to snack on, not the Mouse Guard with sharp swords and the will to fight back. How many meals are worth losing an eye over? An ear? The nose you use to find food? How about getting a sprain that leaves you limping for a month?
Maybe the beast is very hungry and starts off the first round A/A/A. But what after their disposition takes a serious hit? Maybe time to throw in a round of Defend or two.
While the smartest thing sometimes involves the willingness to go all out, rarely is anything living able to do so, or so motivated. It’s how a few armed folks can keep a mob at bay. Mouse Guard (as a comic, and as a game) is very much that tension of a dedicated group to the ideal of the greater good, in a world full of other mice and creatures that operate on self interest.