Any time there is a detour, or a construction zone, or a traffic accident, or a road flooded, or whatever else your route data is not just "worse" it is completely wrong
it's true, but if the scenarios are rare you can treat them as outliers and have the vehicle switch to a "safety mode" or similar. Even human drivers effectively do that (or should!).
Any time there is a detour, or a construction zone, or a traffic accident, or a road flooded, or whatever else your route data is not just "worse" it is completely wrong