It ins't a typo, it's feature.
There are many ways to detect enemy tunneling. Soldiers have been doing it forever. With detection electronics, any tunnel can be triangulated by the sound the diggers give off as they bore into the ground. Modeling the underground using sound is a technique older than this century.
One solution for enemy tunnels is equally ancient but still germane, counter tunnel using sonar to find them and technology to kill them. Back in the old wars it was by introducing high explosive or combustion gasses to the enemy tunnel. Now? Acoustic technology is a 1000 times better.
How hard was it to put a probe into the enemy tunnel and flood theirs with lethal gas? It's a quiet end to a miner problem