I’m guessing test and prod are highly-segregated to prevent improper data access. Remember when one of the app-based taxi companies had employees who spied on their exes via their system? I’m guessing they beefed up security to mitigate the insider threat risk.

Regardless, your point still stands. The product manager should have gone through whatever process was needed to pull down a limited set of production data to test against. Or the engineers could have logged exceptions in prod before making the filter active.