So long as joints are intact and transferring weight level ,the track is floatation for the cars.
Weight plus grip = traction. The track prevents sinking or digging in of a wheel or wheels.
Sanding is helping grip to keep drive wheels from slipping as much.
It works. Kinda like temporary corduroy road work where small logs or similar grant the floatation.
Or a bridge or raft's or snowshoes or cross country skis displacement. l.o.l.