There are three iterations of these weapons; the Blades of Chaos, the Blades of Athena, and the Blades of Exile. The first are taken by Ares, and the second are destroyed and remade as the Blades of Exile. So, theoretically, Kratos should be wielding the Blades of Exile, not Chaos. However, for unknown reasons, the design of the blades in God of War (2018) is based on the original iteration, all the way back from the first game.