Well, it does make perfect sense. And you explained a lot of it in your article you posted the link for. We know the moon affects the tides & quite strongly at that. It's an awesomely powerful force that can govern the oceans! There have been documented studies that are well respected by the professional community that when the moon is full there are more accidents causing pets to have to visit the vet or ER. It's a fact. The #'s prove it. More babies are born. The #'s prove it. If you think about it logically; it makes perfect sense that the sap would be rising when the moon is waxing & therefor the fence posts would be full of moisture.
People like Aunt Bett & Ninna didn't need scientific studies to tell them these things were true; they saw the evidence with their own eyes. For hundreds & hundreds of years observations were made & conclusions drawn & time bore out the truth of those conclusions. These people relied on these things they or their forebearers had learned in order to live; to grow food so they could eat & to fence their plots & build their homes. This was not just old wives tales or folklore or gibberish or superstition. These things had been proven over time & the knowledge was handed down from generation to generation so the future generations could live & be fruitful. We do well to heed the lessons of generations that came before us. They are the learned ones.