Let's be clear here...the iPhone XS Max is NOT waterproof; it is water resistant:
Splash, Water, and Dust Resistant3
Rated IP68 (maximum depth of 2 meters up to 30 minutes) under IEC standard 60529
source - https://support.apple.com/kb/SP780?locale=en_US
A crack in the glass makes it that much less resistant so I would not assume it will handle the same conditions as originally spec'd.