I think (and what follows is highly controversial, so I’m prepared to be shouted down)
that Peltasts would lob and ‘pelt’ the enemy with masses of javelins at very short range,
evading enemy charges by using their greater speed and distance to run away if charged,
and only charge in themselves if their javelin barrage disrupted and disordered the enemy.
Thus there were three distinct types of infantry in ancient times:- Heavy Foot
= such as Blades, Spears, and Pikes, that could only fight in close combat. Missile Foot
= usually light, such as skirmishing Psiloi (but also close formation Bowmen),
that wanted to fight at a distance and avoid close combat. Medium Foot
= such as Peltasts, that could do both, depending on the situation.
There is some evidence that even Imperial Roman Auxilia fought as Peltasts, as described
by the ancient historian Arian in his account of the Battle of Mons Graupius in 84 AD,
where the Caledonian Warbands occupying a difficult hill were met by Roman Auxilia
while the Legions stayed behind in reserve:-
“The battle began, and at first was maintained at a distance. The Britons wanted neither
skill nor resolution. With their long swords, and targets (i.e. shields)
of small dimension,
they had then address to elude the missive weapons of the Romans, and at the same time
to discharge a thick volley of their own.”(Source: www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0132%3Alife%3Dagricola%3Achapter%3D36 )
Unfortunately, the DBA troop classes has no ‘lob missiles and evade if charged’ troops.
The nearest equivalent is Psiloi, who flee when doubled by heavy foot.
So the army lists have to use Psiloi to get the Peltast effects.
It’s a case of bending history to fit the rules, instead of creating rules to fit history.