It all boils down to two things:

What was the predominant hoplite style fighting?Overhand.
Did they use underhand on exceptional occasions? Certainly.

We all agree on the exceptions you've put forward, which are well based, but you cannot seriously think that 8000 hoplites in a battleline would charge without any spacing between them, or that the synaspismos would work perfectly all along the line. Some hoplites would have spacings between one and another, allowing this and other kind of movements.

This is exceptional and utilized when the conditions allowed it. How many times do I have to tell that?