With cars we have technologies called roads and lines and signs that tell us where we can and cannot go. But sometimes, those fail us. Particularly in areas with lots of dirt roads (no lines). And especially when there are many dirt roads (potentially no signs, too many locations to put them up). That does not excuse people from driving in restricted areas. It may be cause for mitigation. But, at least around here, driving in an otherwise unmarked (signs) wilderness protection area (on the map), will still get you a ticket and a fine if you're caught. Even if you did pass into it on a dirt road you were allowed to drive on and there were no signs.

The pilot can try that line of reasoning, it is (somewhat) valid. But reviewing maps would, ideally, only be made redundant. Since we don't live in an ideal world, it'd still be their responsibility to know where they were flying.