The Cause was because it fought in a super-tight formation of shields and spears (or axes): a Phalanx. The Cause however is not necessarily because the unit was deeper than the norm, i.e. The Effect in TtS can be whatever the 'Deep' rule entails: greater staying power but penalties to maneuver. The Theban phalanx at Leuctra is still Exceptionally Deep (or Exceptional Phalanx) as per rules. Note: Pikes are already depicted with at least 3 ranks of miniatures and have their own added benefit. The other Phalangites who needed extra depth beyond the norm to compete are depicted with 3 ranks of miniatures. Spartans) didn't need extra depth beyond the 'norm', so are depicted with 2 ranks of miniatures.

*It does still simulate the distinction between better hoplite/shield wall Phalanx troops and those who went deeper to compete with the former. it's lumping them all rather neatly together and somewhat blurring (*see below) the distinction. It won't please those preferring the flexibility offered by the regular and deeper formations where the latter get a bonus to their resilience (with penalty to maneuver), but it does prevent those in regular depth from avoiding penalties to maneuver at the expense of extra staying power. Not some added depth to the formation beyond 6-12 ranks. So this is saying that it's their tight formation (wall of sharp pointy things and shields + specific training) that provides the staying power and reduced maneuvering. Note: if depicting Hoplites in 3 ranks, Pikes would look better in 4.

Hoplites, Pikes and Shield Wall still benefit from their own idiosyncratic bonuses as listed in the rules. Pikes may be depicted on the table with 3-4 ranks of miniatures. Hoplites and Shield Wall 'Phalanxes' may be depicted on the table in 2-3 ranks of miniatures. Works the same as 'deep' with extra staying power and worse maneuvering. Hoplites, Pikes and Shield Wall all count as 'Phalanx'.

Hoplite shield wall