I always saw the spartan 3’s as soldiers with fancy equipment rather than super soldiersI think you're thinking of Spartan 4s mate.
S2 are children brought up as war gods, with best genes and discipline.
all rare and above average gifted and expensive.
Long 6 years training
S3 are street kids teenager trained to half-god.
A naive cannon fodder for revenge. A few are outstanding.
A few years training.
S4 are ambitious professional soldiers equipped with a god-power tool.
Adults doing military careers.
Volunteer soldiers who have proven themselves in combat. All they need is a Spartan armor and luck with the agumentationsa.