Why would you want to? Is there anything remotely _that_ important where you have to take your new XR iPhone in the shower with you? Why risk it.
How do you wash properly with one hand only if the other is busy with your phone?
Good grief. What an odd product. How many hours do people spend in a shower these days?Maybe they were considering this..,
Officially, that is correct but my friend had water damage to his iPhone X and the Apple store replaced it due to a faulty earpiece seal (moisture was being trapped between the glass and display). It's case by case, if water damage is secondary to a manufacturing defect they generally seem fine with fixing it.Pretty simple. Apple doesn't cover water damage. There is your answer.
I always use my phone in shower since the water resistance added in iphones. Never had any issues. But make sure SIM card tray is properly inserted.