The US Vest, which consists only of a PASGT armour vest, apparently offers zero ballistic or explosive protection.

Meanwhile, the Vest (M16 + M203) (Airborne), which consists only of an unarmoured load-bearing vest, apparently offers a moderate amount of ballistic and explosive protection. Similarly, the SF Vest (TLBV), which is also a load-bearing rig without any visible armour, has a ballistic protection rating similar to the vanilla Raven bulletproof vest.

It's unclear whether these are issues with the Arsenal protection rating display, or whether the actual armour values of these vests are wrong.