What does the reviewer Septicemic mean in that you can pick your team in the scenario "Advance of Antonius"? ie your culture, or your player number?

In reviewing the scenario "The advance of Antonius", Septicemic wrote: "Being able to choose a side is a good feature, but did create problems of imbalance, due to lack of control of so many units, so disadvantages couldn't be countered effectively depending on the player you chose."
You can find the .SCX scenario game file, along with his review, here:
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How do you "choose a side" in this scenario?
In Single Player, the game only gives you the side of Player 1, Vespasian, in Blue.
I guess in multiplayer you can pick sides, so I thought that he might be talking about using it for multiplayer games. But I assume that choosing your side is a typical feature of multiplayer games, not something unusual or special, so I don't know what he means when he calls it a "good feature" in this particular scenario.

I think that he was talking about Multiplayer.