Every sign has a purpose. A stop sign has a purpose. What is the purpose of that sign?
True, the court would not invalidate the sign. It would have to be fought with those who posted the sign.
Most of that parking lot should allow back-in parking. Therefore the sign should be more specific, or not be posted at all. IOW, the sign amy be in error and should be removed. If it was put up in error it should be unenforceable.
Again, it would take a skilled lawyer and a lot of time to undo that citation. But in theory, I believe it could be done.

