The article provides evidence of ridges formed in desication joints during the seasonal wet period of the dune field. They are not obvserved during the dry months. The cohesion of the wet sand in the joint allows it to stand in relief after wind scour of the dryer sand. I've seen similar structures formed on sand dunes by pouring water on a dune at night and observing again in the morning.

But you are right, and I agree, the raised joints in Mars sulfates seem cemented, not wet, and are of a different composition than the surrounding unit. While the impact induced joint is likely, I can also see how desication structures might create cemented joints.

Picture this big pile o' sulfates during the diagenetic phase. Water (brine) is moving upward through the pile. On the surface, when it is wet, there may be small, shallow pools. During dry periods, cracks form. If this happens cyclically, then these fractures may become conduits for fluid movement in later wet events. Especially if some other material falls into those cracks.

Once the whole thing starts to really dry out, the pile forms wide scale desication polygonal fracture patterns. The sediment above drops, or is pushed, into the cracks. If the strata above is a different composition, when so will the crack filling.

Similar things happen on earth. I've seen sandstone dikes that are interpreted as sediments injected downward into granite.

Are we seeing a similar process right now? Cracks in the bedrock being filled with sediments?

Just some afternoon armwaving.