ip rating is just a number. with ip rating , it does not guarantee you can wash or submerge the phone under water of 1m for 30 minutes. phones with ip rating is much higher in price it only due to they need to do a water seal test for each unit before packing, this takes up production cost and time and need to set up a water test production arm, and also need to pay licence for using ip rating. When the phone pass the test, doesnt mean that it will be confirm water resistant, that y the phone manufacturer will not warranty for water damages. water dameges could still happen even if you just run your phone under the tap for 5 seconds.

The cost of doing ip rating will make the phone more by usd 25-35, which is a lot if you compare with the whole cost of manufacturing the phone.

For some phones basically they did the same thing as the phone with ip rating, with rubber sealant at places, but they decided not to spend on doing a production line just to do the water test and which will make the phone cost goes up significantly. This phone can be also at ip 68 rating, but they choose not to do the test because of cost. the only downside is that they cant market their phone as ip 68.