It would seem there may be some merit to this. I have observed meats that shrink more when basted with a rub high in salt. It probably draws out the water or liquids and dehydrates them more rapidly and removing the water makes the food appear to shrink...I think I have observed this in cooking lots of different foods.
Yes its true, because salt takes moisture (natural juices) away, thats why dried fruit is small and shriveled, because the moisture has been taken away.
But there might be a few exceptions on what foods are affected
