Generally, it’s up to the person or body that’s disputing the status quo to prove that it is erroneous. Otherwise you’d have every man and his dog claiming bits of property that weren’t theirs. You would expect the OC check the facts when they were challenged before they started hiring lawyers to defend something that might be indefensible.
On the other hand, if they had information that contradicted accepted views, you’d expect them to pursue that issue and for the individual owner concerned to start looking for evidence to the contrary.