The corrective agent has the exact same percentage chance at making the mistake. "Correcting" an assumption that was previously correct into an incorrect one.
If a singular agent has a 1% chance of making an incorrect assumption, then 10 agents have that same 1% chance in aggregate.
You are assuming statistical independence, which is explicitly not correct here. There is also an error in your analysis - what matters is whether they make the same wrong assumption. That is far less likely, and becomes exponentially unlikely with increasing trials.
I can attest that it works well in practice, and my organization is already deploying this technique internally.