Aha. Visual to tangible translation error. I intellectually know cattails are in stands, but tend to interact with them, hands-on, one or maybe two at a time, rather than seeing the entirety of the stand visually. It's a trickier reality to get a handle on than, say, a forest of trees as interconnected; those are far more audible. Whispering in a marsh could be any and all sorts of varied grasses.