The same way they use durable glass and don't cover broken glass under the warranty.
If I drop my phone on the ground screen first, I have an idea that it might not break, but it might break. If it doesn't, I'm happy it survived, and if it does I don't go out and sue Apple.
Same if my phone gets hit in a rain storm by a bunch of drops of water.
Car crash standards are okay, because the car always crumples, and they don't make promises like "you can crash a car at up to X pressure and the crash will not penetrate and cause damage". If a company was parading third-party lab results showing an immunity to 10mph collisions vs. walls, their warranty has no place excluding 5mph collisions vs. walls.