John's explanation for sandy whoops is exactly right. However, sandy whoops require a different set-up than rocks, ruts, and roots that you find in most woods areas. On rocks and roots, you want the suspension to compress fast or you will get beat up and worn out. For a plush ride in tight technical terrain, you want less high speed compression damping.
Sounds like your riding area has a little bit of everything, so you are going to have to experiment with what compromise works best for you. IMO most MX bikes work best with less compression damping and more rebound damping in the woods, but sand whoops are a different story.