Why does Apple claim IP68 water resistance when it clearly is not?

Note the same is true for all manufacturers.

It's like the stronger glass on newer phones - it increases the odds of the glass surviving a drop intact, but if it falls "wrong" it can still shatter just falling off a desk.

The rating means it passed certification tests in laboratory conditions. This means the water wasn’t chlorinated.

The 2 meter depth for 30 minutes is how the phone was tested, not a suggestion for real world use.

Water resistant does not mean waterproof.

Apple suggests you do not submerge your phone, swim or bathe with it.

See this:

https://support.apple.com/en-us/HT207043

What you think is irrelevant.

No phone manufacturer covers water damage on any phone that is water resistant.

All of them advise you not to submerge the phones in water.

You destroyed your phone by submerging it in chemical filled water.

Buy a new device.

Additionally, RTL 44, as Apple warns with the new iPhone 12:

«Splash, water, and dust resistance are not permanent conditions and resistance might decrease as a result of normal wear. Do not attempt to charge a wet iPhone; refer to the user guide for cleaning and drying instructions. Liquid damage not covered under warranty.» (emphasis added)

I’m sure they had similar warnings for the iPhone XS and XS Max.

So it would seem to imply, RTL 44.

However, as always, one must pay attention to the “fine print”.

As they say, caveat emptor: let the buyer beware.

Particularly in this case, Apple has no control over how an individual’s use of their product will decrease the water and dust resistance of their product.