You can propel a boat forwards with only one oar, without lifting it from the water. It's a useful skill, Kayakers use the same stroke to move sideways, and for stability in rough water. See https://en.wikipedia.org/wiki/Stern_sculling
Exactly, that's why calling this concept nonsense is so weird. It might be a tiny bit counterintuitive at first glance, but there's plenty of examples of it all around.
