Well, that's arguable since, for example, Kyrene attempted to take over Egypt together with the Seleucids, and Syracuse had long tried to rule Sicily and Magna Grecia. EB1's faction list is not the only possible selection, even when using the same criteria.
That said: I agree that, at this point in history, the Greek colonies weren't particularly more aggressive than other cities. Creating a special faction for them would suggests that there weren't other minor players attempting to start their own little kingdom in the shadow of greater empires.
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