I’m not a geologist, but I am very familiar with slickrock and slot canyons. And it seems to me the basic patterns are consistent with sand deposited by wind, not by water.
Or at least I’m not familiar with any underwater dune formations hundreds of feet high.
Perhaps there are some in the scab lands? When the ice dam broke and 500 cubic miles of Lake Missoula abruptly drained to the Pacific, a lot of material got moved around. Happened some 40 times...