The article explicitly says that equal areas are not required for fairness; and gives this explanation for wanting equal areas: "Dice that are fair by symmetry

The article explicitly says that equal areas are not required for fairness; and gives this explanation for wanting equal areas: "Dice that are fair by symmetry (and hence under any reasonable throwing dynamics) always have to have an even number of sides and belong to certain symmetry groups (Diaconis & Keller 1989)."