If you open a Qilin (Unarmed) or Prowler (Unarmed) in the Editor vehicle customiser, it will appear to have the minigun or HMG turret and additional ammo crates afterwards (and the commander's MG in the case of the Prowler). The turret appears when the vehicle is initialised after being modified, for example by copying and pasting it or by reloading the mission in the Editor.

There is no apparent gameplay impact and the additions are not visible when actually playing the mission. Vehicles affected can still be filled to their unarmed capacity with passengers, despite having some seats visually blocked by crates.