Absolutely. Confusion/befuddlement is the biggest asset, in particular when nearly all people wind up with pin-point focus when in the fighting zone.One advantage a duel-wielder has against an opponent using a single weapon is that the latter has to keep track both of your weapons during the fight. So your opponent constantly has to shift their attention from you to weapon A to weapon B and back again at all times. And people aren't very good at doing this in a fight.
It's certainly not actually quicker - you can thrust many times with a spear in the time it would take to attack with one weapon, then the other. Heck, you could hack twice with a two-handed sword in the same time.
It's not speed. It's defense and distraction.