I don't think lowering the tire pressures in that situation would have helped as it was already riding the skid plates.
Sand is my major concern here in Southern California. I think some of the limitations created with the non full time 4x4 also led to it getting stuck in the first place....loss of momentum. That and it's ground clearance compared to some of the larger vehicles with full time 4x4's make it a bit more restricted in certain terrains...sand.
I guess it's just a trade off for some of the other niceties and efficiency of the Trailhawk.