"Treyarch said!" That's a piss-poor source of information, I hate to tell you guys. Look at what the PC guys go through. Also, the list was out before map was released. Could've been a bug they thought they could work out at the time the list was created. It was probably Type 99/sawed off vs deadline. Deadline won. There are many other plausible explanations such as limits of the game engine, etc. that seem more likely than any scheme I've heard so far. All things considered, I'll believe it when I see it.
Oh and it would be there (in the box) the whole time like all other weapons, like all the other maps. There is a small chance they whipped up some crazy script to allow for guns to be added to the "master list" during mid game. What other guns did you have to "trigger" in any previous map? None. And you have to jump through hoops to get availability (no guarantee) to a gun which is inferior to others already available? C'mon, be serious. Like I'd trade my mg42 or waffle for that POS.
*Don't tell me how strong it is against zombies, you've never used it!