The Makedonian phalanx -- why such depth?

[Paullus Scipio]

It is well described in the manuals, but since we are here discussing Greek Hoplites, there are a number of references to 'normal/open' and 'close' order in Xenophon...

And Xenophon has exactly what to do with the Macedonian phalanx? What exactly does supposed Archaic and "classical" hoplite "drill" have to do with the Macedonian phalanx? This being a phalanx that the sources clearly differentiate from the classical city state phalanx.
It is readily apparent from our sources/manuals that Phalanx drill, both Greek and Macedonian were evolutionary in nature - indeed the manuals say so.Further, it is not I who have taken the topic of depth from Macedonians to Greeks and back again, though given the evolutionary nature of Phalanx drill, it is understandable that the participants have included references to both. We could just as easily restricted the discussion to the Macedonian Phalanx, with a mere acknowledgement to it's Greek ancestry. Clearly you are not familiar with the manuals.
It is clear, to me at least, that the "Macedonian phalanx" was a different critter from the city state hoplite muster. You, though, insist on equating the two. Worse, you aduce Xenophon's fiction of the "Cyropaedia" - Asians as Greeks...well at least the "good" Asians.
Not equating - one all too obviously evolved from the other.

The bottom line here is that we have a clear description of the effect of a Macedonian phalanx "when sixteen deep" that you insist on being rendered as eight.
Because that's what the evidence points to....on the one occasion we are actually told the depth that Alexander's phalanx actually fought in, it is eight deep.

I fail to to see it still. Your demands - from others - for a wholistic "hypothesis" explaining all ancient sources, which are most unforthcoming, is no ipso-facto substantiation of your own flawed hypothesis based on stretched, scant evidence.
You are welcome to your own "flawed hypothesis based on stretched, scant evidence", if you have one ! So far you haven't put one forward. Mine at least has the merit of fitting all the known facts, and I've yet to see a better one !