Armor protects the wearer from every damage source. It shouldn't prevent damage for suffocation, drowning, falling, my least favorite, fire, and falling into the void. To produce, have full diamond armor and most of the times, it prevent you from getting any damage at all. Fall from a hight of 23 with and without armor without the bug, it should kill you both of the time b/c 23 - 3 = 20 damage = 10 hearts of damage.