i tested all the armor sets and they all act like unenchanted diamond armor. i take half a heart of damage when I get hit by a zombie while I'm wearing each of these full sets unenchanted

Half a heart is minimum Damage you can receive by Minecraft design.
gotta correct that:
Damage taken can go below .5 but never nothing. It is stored exactly but rounded for the health bar.
for details see minecraft mechanics: https://minecraft.fandom.com/wiki/Armor#Mechanics

i read it and melee attacks do get reduced by armor. i went back onto atm6 latest version and wore full atm armor and I did not take any damage from mobs

Put an atm,vibr,or unobt jet pack on ;P