I don't think that that's necessarily the case.
The attraction from WOW's point of view is that it would give them the base for extending their highly regarded Big W operation to NZ with the buying power and other synergies that it would bring.
It may well be, too, that Foodstuffs would be more relaxed about WOW buying out WHS if they consider that the WHS chain won't be used to compete against them in the food business.
;)