There's a much more accurate parallel here than licensed software. Open up any paperback book to the publication page. On it you'll find text similar to this (found in my copy of "The Pelican Brief"):
If you purchased this book without a cover you should be aware that this book is stolen properly. It was reported as "unsold and destroyed" to the publisher and neither the author nor the publisher has received any payment for this "stripped book"
The guys at AutoDesk said "you don't need to ship that back to us, just destroy it" regarding the old versions R14. They did this to save money and allow cheaper upgrade pricing. After shaking hands on that deal those R14 disks, if sold, seem to me more analogous to stolen property than previously licensed editions.