IP67 and IP68 are considerably different. It’s basically the difference between water-resistant and water proof. IP67 could handle splashes of water and, at least on paper, brief submersion. In reality, most. IP67 phones did not handle any level of immersion well.
IP68 on the other hand allows phones to be submerged deeper in water and for much longer. You can have IP67 with those features, but IP68 is a different beast.