specifics in Spear fighting combat

[PMBardunias]

an overhand thrust (thumb toward sauroter) its a little tough on the wrist, and the range is a little less because you tend to thrust more down than out. but it does have aittle more power

The downward T-T-S thrust can be very powerful as you mention because you can bring your weight behind it like chopping with an axe, but there are other advantages. The first has been mentioned and would be enough on its own to mandate it in the phalanx: you won't injure anyone behind you.

Additionally, no other strike gives you the same range of lateral targets. You practically have a 180 degree arc in front of you covered just by rotating the wrist. You also have more targets since a side-arm thrust will always come in on the shielded side of your opponenent.

If we take into account the aspis, then this strike has the greatest reach. The round aspis, pressed to the chest in formation, or held a bit away if not, will interfere with a stab delivered sidearm at its widest point. To counter this you have to uncover the body with the shield to get it out of the way.The overarm thrust pushes the whole arm over the rim of the shield.

You may read that hoplites stabbed standing sideways with the shield up resting on the shoulder facing an opponent. This is drivel spawned from a lack of either experience in combat or a course in functional anatomy. I have read this described as "like a fencer", though the author must be unaware that a fencer LEADS with his right and the weapon. Striking over one's head and across one's body is a joke, no matter what some sculpture shows. Squaring to strike, then jumping back is fine, but it negates most of the benefit of hiding back in the first place. Simply leading with the left foot rather than standing perpendicular to your opponent is more rational.