I think the use of the Force is part of the lightsaber duel. Obi largely beat Vader by throwing rocks at him. Vader beat Luke by throwing things at him (at least greatly weakened him).
I'd say using the Force in a lightsaber duel is no different than a kick or headbutt in a sword fight. It's still a measure of your skill and ability. It almost makes Mace even more impressive because he really only ever uses the lightsaber and only the lightsaber.