We hired an engineer who aced every round. Two weeks in, on a payments service we'd inherited, his retry fix double-charged test accounts in staging. Not really his fault, we had tested writing code and never once tested reading someone else's.
Now the trial task is a repo we didn't write: tell us what breaks and why. Harder to grade, and different people pass it. You are hiring either for writing or for reading, and those turn out to be two different things.