It was not a 90% error rate (or at least that’s not a claim I read). It was that 90% of appeals of those decisions were decided (at least partially) in favor of the appeal. That could be 1000 decisions, 10 appeals, and 9 reversals.

I am personally 7 for 8 in lifetime wins in my city's parking ticket appeals process. That doesn't mean that I think that 7 out of 8 tickets my city issues are incorrect.