I don't believe it's a UI issue at all. It could just be that it was coded incorrectly for the desired mechanic and the patch notes are correct. Or, conversely, it was coded correctly and the patch notes are incorrect. So either it's a bug in the first case or a miscommunication in the second.Not sure there's a UI issue in this particular case, just an inconsistency between the patch notes and the game play. Regardless, the core questions here seem to be "Is the current mechanic better as is or would it be better if it worked as described in the patch notes? Or is the difference too insignificant to matter?"
The impact is likely minimal, however if it was working correctly per the patch notes it would add an incentive (however small) to build city defenses.