Why doesn't Jonas tell his friends about his training in The Giver?

The Chief Elder has told Jonas that although his position is a great honor, his training will be alone and apart.  And, when Jonas receives the instructions for his assignment, they contain 9 important directions.  Number 4 clearly states, "Do not discuss your training with any other member of the community, including parents and Elders" (Chapter 9).  Jonas also realizes that, even if he were allowed to tell, his friends, who do not have his gift, would never understand what he was talking about. What he is learning is too far out of their own experience.