Body Armor is +2 in the 2005 rules as well. It seems that you're looking at the creation rules, not Chapter 3 where Body Armor is explained.
Technically, a Minifigure's Armor Value is 1d6. With bonus dice from rolling a 6, the average roll comes out to be 4.2 or something. The basic Minifigure just has a value of 4 because it's expected that you'll be using a lot of them, and instead of rolling Armor every time they're hit, just use 4 instead of 1d6 and it will save some time.
With Body Armor, a basic Minifigure would have an Armor Value of 4+2, or 6. If you want to roll, a basic Minifigure has an Armor Value of 1d6 according to the MoC Creation rules, or 1d6+2 with Body Armor.