What did the US Geological Survey note regarding features previously classified as grainflows?

They are now better explained as products of water activity

The interpretation of Martian geological features has undergone a significant recalibration. Features that were once ambiguously categorized, sometimes attributed to slow-moving lava flows, or specifically identified as grainflows—sediments transported primarily by wind or gravity—are now being reassessed. The US Geological Survey has specifically indicated that many of these grainflow interpretations are more accurately explained by the processes involving water transport and deposition. This shift in understanding strengthens the overall case for a pervasive, active hydrological cycle during Mars's ancient past, as it suggests water was a dominant geological agent reshaping the terrain.