You are confusing the Sabaean bodyguards with the nobles. The Bodyguards are the ones with swords and brown coats, and they accompany the Sabaean FMs in campaing. The nobles are the armoured ones with spears, and are normally recruitable.
No I'm talking about a picture I saw on images that had sabaens in the armour of the nobles but holding a sword. So I suspected that it was an old version
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