I think it would properly be termed a "shieldwall", a formation of great and respected history that stayed in use until pikemen eventually replaced it during the Middle Ages. The old Greek hoplite shieldwall (which might've been loaned from the Assyrians whose wall reliefs picture similar formations), although such formations also tend to get referred to as phalanxes, wasn't the Macedonian pike phalanx (which is what RTW means with "phalanx"), but on the other hand it could be argued that Rome's phalanx mechanic with shorter spears and shields (such as encountered with Royal Pikemen and the German Phalanx) is actually a better representation of the shieldwall that MTW's "spearmen in Hold Formation" thing.

But then at least the Triarii should be able to do it too, if you take that approach...