When the recruitment officer arrived from Greece (possibly Cape Tainairon) in the winter of 256 BC, he arrived with around 50 - 100 Greek mercenaries.

Polybius doesnt tells what this Greek mercenaries were, but I assume they were probably hoplites.

Because they were so few, because they were mercs, because of their number, and because of the engine limitations, we tought that the best way to represent this troops was to made them the bodyguards for Xan.

I think that nobody here wants Xan using a Sacred Band Cav as bodyguards like the other Carthaginian generals. Giving Spartans, for a Spartan general was the best option in my mind.