From my understanding, they made so much of it and expected to release another "wave" of 05-06, but that never happened and they had a bunch of the autos etc leftover that was never released in the 05-06 so they added it to 06-07. I guess that's what happens when you make tons and tons of something and it doesn't pan out the way you think. I'm not 100% sure if that's what happened, but it sounds logical to me. I can definitely see UD trying to make the most they could especially with stellar rookies like Crosby and Ovechkin in the same year.
I also did manage to pull a Staal Future Watch auto out of the few boxes I did open of 06-07