Read carefully. They might say Orange Juice on top and 100% juice on the bottom. The consumer is lead to believe that it is 100% orange juice but they are only indicating that you are buying orange juice and the product is 100% of various juices.
apple juice is a filler juice for most juice and probably add a natural sweetness to tart flavored juices.
Apple Juice is the base juice which is added to almost all juices. It might be something to do with that.