So I'd say the official Anker position would be a very polite non of your business, which in reality means they do not reply to the question as you don't need to know. They sell a product with stated specifications performance size and an 18 month warranty so the innards is their business.
There are tear downs out there. The general trend by Anker from the tear downs seems to be a bit away from the 18650B Panasonics Li Ion to Li Ion Polymer. You can see this with the trend of the cases from round or round sides to more rectangular.
I expect the main benefit of this is more of a higher input and output rate, probably a bit less warranty issues with the cells balancing where one bad 18650 drags down the total power.
The move to Li Ion Polymer means the casing of the 18650 with just a thinner external casing by Anker must move to no casing from the polymer to a tougher casing by Anker. If you know your engineering, a bigger casing must necessarily be thicker due to torsion, so I expect a bit bigger for a given level of safety.
My theory is you see all of this in the Powercore II with its less than stellar density, its impressive 6A output for only 20Ah, and its square sides.
Anker in social media have hinted at more USB-C, so I expect it will be driving move to polymer to get smaller items to deliver more Wattage. Details are scarce but that's what I think will be one major theme through 2017, the Wattage you see in the bigger batteries coming into the smaller batteries.
It is very reasonable for this to be internal and close to Anker as it is their business, their announcements, their need to surprise competitors.
Personally, I'm interested, but I don't care. It's only a battery!