I keep wondering if the cards would all have been over-powered if they simply set to "day" (or "night") instead of this wordy conditional version?
Yes, it would have made switching easier, but IMO that's a plus because all these cards depending on day or night switching a really weak if you can't make the switch often enough to be worth it.
It's likely less about power level of these cards, and more about ensuring they don't screw werewolves over by making the switch back to day too trivial.