I don't think they meant it that way.
Well, obviously not daggers, but I think they actually mean that you can opt to use both your hands on your katana, for instance, for a while to deal some extra damage. Change to one-handed, use spell, change back to two-handed, etc.... sounds cool..... and maybe there's different coups de grace for one-handed and two-handed?
No, Silverglade, that's not the case. Here's the original text:
"Man kan for eksempel bruke et etth?ndssverd i to hender for ? ?ke skademengden"
One can for example use a one-handed sword in two hands to increase damage amount.
You can use a one-handed sword in two hands to increase damage. No way to twist it to make it otherwise