there purpose was to hold not to kill, and without some from of infantry or cavalry back up were eventually overrun (as we see on the left flank in Gaugamela). That would explain the strategies of Pyrrhus when he split the phalanx with close-melee troops. But they were use to aggressively pin an enemy (the only defensive formation was that which fortified a position - all others had to be used aggressively lest the enemy simply flank).

You need to define your terms properly, before you begin to define things with them.

Foot