Beat the Grass to Startle the Snake
Your opponent has a snake hidden in the grass. You know it's there, you just don't know what it is. So you make a probe move to startle the snake into moving. Then once you know what his plan is, the snake is not a hidden threat anymore. I'm sure you have been in lots of tense fights before, where the reading is very difficult. Does your opponent have a snake in the grass, waiting to strike? Knowing is half the battle.