Query re 4th level Paladin Spell: Holy Sword

[Dannyalcatraz]

I have a 2WF Paladin...her off-hand weapon is a spiked shield, though.

 

[Plane Sailing]

Maybe it is a holdover from the 3.0 version of the spell, where your 'holy sword' did double damage on all attacks? I could see them wanting to limit *that* to just one weapon.