As things stand, Le Yin could simply walk away after snatching Ming Shuiyun, even abandoning everyone wouldn't be a problem.
The reason he worked tirelessly to disperse the sword scabbards and prevent them from fighting each other was precisely to create an undisturbed environment for cheating—cheating outside the exam hall is difficult because transmitting answers is easily interrupted, just like when the cheaters playing a flute duet were battered by a suona played by the Cicada Dust. If Le Yin used firearms to transmit answers, it would be like hanging a sign on himself saying "Come disrupt me if you dare".
