Boomer deliberately throttles the assault so the trapped enemy believes it's a stalemate and never surrenders.
Taking command of the assault, Colonel Boomer tells the troops to stop celebrating: nobody fights harder than someone that's trapped. He orders them to form up but not push too hard, because a surrender would end the fight on the enemy's terms.
The goal instead is to make the enemy think it's a stalemate, keeping them in place—and keeping a few of them dumb enough to keep jumping into the Acid Trench. Boomer gives the generals maybe half an hour before the enemy either escapes or has to be wiped out to the last, a clock that runs directly against Carl's raid on Empress D'Nadia.
The deliberate tempo control that buys Carl time to reach the enemy empress.