From a mechanical perspective ip68 is perfectly achievable mechanically and watches have been achieving it for a long time, however… with what sort of margins for the manufacturer and what sort of cost for the consumer ? Additionally a lot of them require pretty carefully adherence to instructions torques and tolerances to achieve the same waterproof rating. Personally I’d be very happy to have a phone that says, if you swap the battery you might lose the ip68 rating unless you follow the resealing process within tolerances.