AFAIK phalanx lines did normally have reserve lines, true. But those weren't pikemen - *they* were all in the main pike-wall.

Also, the "fog of war" appears to often have made it extremely difficult for officers to know if and when they should move up to support the pikes or, indeed, what was actually happening at the front to begin with; didn't really help that the supreme commander was normally somewhere in the wings leading teh cavalry...