My assumption here is that the PASGT is modelled in Reforger as a singular kevlar material, whereas the 6B2 is titanium zone + underlying kevlar on the front with only kevlar on the back.
So it seems like the PASGT is performing similarly to the current live version of the game, whereas the 6B2 is performing noticeably worse.
This leads me to believe that the 6B2's titanium plate is not calculating intended armour resistance. However, if you shoot the 6b2 at an oblique angle, it still offers deflective properties, so it doesn't appear to be the case that the titanium plate is non-existent in the calculations.