This is a picture of frightened Spartan hoplites trying to survive – not men Leonidas would admire. We’re getting an early picture of Spartan tactics before the Lycurgian reforms had taken hold.
We know that the Spartans fought poorly in the battle against the Argives in 669 B.C, so at some point after that (perhaps 650 B.C.), the decision was made to re-distribute land and build a real army. Unlike the changes to the government, the Spartan battle tactics took time to develop. Generations would have to pass through the agoge before the fighting machine was tuned. The Spartans were defeated at Tegea in the first quarter of the sixth century, but triumphant against the Argives in 544. Finally the Spartan phalanx had achieved superiority.