A sword swing to thea head will always 99.9% will cut it off, arm aswell and a strong individual like Geralt in this case that he could have potions or enchantments on the sword is more plausible to chop off limbs regularly.But it would be unrealistic. I don't know if you've ever read the manga "Berserk" by Kentaro Miura; well, in the scenes where Gatsu (the protagonist) shot the monsters with his crossbow, the arrows always pierced the eyes of the targets or went inside their mouths. Now in a page it can happen, in two pages you can say it is a coincidence, but in ALL the story it is too much. It doesn't look like a casualty anymore.
The people who perished by sword weren't always mutilated: throat-slitting, belly and heart thrusting and arterial cutting were also likely to happen.
That in universe is realistic IMO.


