That’s a sampling bias. You are confusing how your metrics are affected by the adverse event with how your metrics are now.
But again, that was years ago. Things may have changed.
Or is it a thing where the client only cares about the default metrics calculated over the full history of an account?
Whether X’s CTR is 10% (what it used to be) or 1% (what it is now) drives the decision of which ad is better to serve in that inventory slot.