The entire book is full of blatant disregards to the rules, inconsistencies in stats, and minor flubs. I love the story behind it, I don't think it's a bad product, but man did an editor completely screw the pooch on this one.
On this same item for instance, the AZT Huitzilopochtli has 15 levels of Concealed Armor (not allowed past ten) and is wearing an Armored Jacket (8/6), but has a total armor of 23/20 (Basic math should indicate 23/21 I believe). In addition the stat line for the body shows 10/10 armor from the armored jacket for some reason.
Personally, I'd just assume that it's SOTA experimental R&D prototype grade borgs and be done with it. After all, given when and where they show up, it's not too unbelievable.