The Surface Mini tablet was once just a tall tale, but a Microsoft Manager has now admitted its existence.
http://www.notebookcheck.net/Microsoft-VP-confirms-Surface-Mini-Tablet.153033.0.html
I would bet the reason was that it would be extremely hard to polish it enough to justify premiums like with book.
At least I was very impressed by these 4th generation surfaces, and the mini would have been simply overpriced with the competition.