The 1 recruit time is there to reflect the eliteness of the Spartans. And I’m also guessing LT made them 1 turn because otherwise Greece would just spam Spartans all the time which would ruin the balance.
Also you should compare stats of different units with different factions. The imperial roman legionnaire is the most elite unit a roman faction can have (until the conquer Roma which means they can get Praetorians!), and they were the finest infantry of the ancient world and the envy of Rome’s enemies. And historically by the time the Romans were the up and coming Mediterranean power the Spartan state was in decline, if you read up on your history books Greece was wanted to become a Roman client state because they didn’t want to be ruled over by Macedon. And I doubt if the Greek city states were not in decline they would have submitted themselves to Roman rule especially the Spartans.