SAMs have never dual wielded in FF games outside of equipping special abilities. In fact, they usually got bonuses or special abilities that enhance their TWO HANDED prowess.

FFT/FFXI in particular:


Hasso: Grants a bonus to attack speed, accuracy, and Strength when using two-handed weapons, but increases recast and casting times.
Doublehand: Wield a weapon with both hands, increasing its destructive power.