as I said in my post: it may depend on the situation at hand; as this is a question of how Hoplites fought in phalanx, we need to establish if overhand use (or underhand), is more relevant to depictions from Greek times of said formation.
In the video he mentions that underarm depictions correlate with depiction of troops in formation. This is puzzling. Now I'll admit that correlation does not imply causation and this could be due to a third factor amongst other things, the question then is, what is the link?

shock (amplifying the initial power of the impact)*? knight's lances also shattered on impact most of the time-yet for some reason, Knights to my knowledge never really came to your same conclusion-at least in general. (the lance was only abandoned because the role of cavalry changed after the middle ages; the latter due to the intro of gunpowder in part, in part from the rise of professional modern armies,and so on)

and yes, whether it is knight or Hoplite, it's the same idea: using you velocity concentrated at a sharp point, well away from you, to poke into the enemy and kill him.

*see friendlyfire's post.
If it was that useful then I'm sure everyone would have used a spear during the initial charge, afterall, its not an expensive weapon. Yet legionaries and earlier hastati didn't use them, amongst a myraid of other troops. Furthermore, a cavalry charge makes significant headway into a formation, so a lot more men can use their lances in a charge. I doubt as many could do so in an infantry formation, in addition, the shock value of a spear is much greater when wielded on horseback.

you also seem to imply that the losing side will just keep pushing-I might be misunderstanding you hear, but that's the implication. they wouldn't-not unless they wanted to die for nothing: if a gap was forced (as in most of these engagements), it would have meant the flanking of the pockets of losing hoplites. those would naturally be seized by fear, and haul it. so any pushing from the losers would stop. unless they're the theban sacred band. it's interesting to note however that much of the killing was when the losers started to run. but even then, you would have to ask yourself: why not be able to kill more of those routing men? and the answer is as I mentioned: once the fleeing survivors dropped their panoply in panic, they could get away from the winning hoppers.
When the front ranks see that all is lost, the will drop shields and run yes? But the mid/back ranks can't see this as easily given that they are more removed from the fighting. They would continue to push, by the time it became apparent that there was a rout, the front ranks would have been slaughtered. More to the point, how easy would it be for someone in a fierce pushing match to simply turn tail and run. They would have incredibly little room, and as soon as they stop pushing, they would be bowled over.

why would that be the case? even if the spear didn't shatter on impact, the hoplite would still be able to plunge it into the 2nd and 3rd ranks-at least in theory. and if that wasn't feasible, then all the better towards explaining why hoplite warfare was inefficient.
This has been my point from the get-go.