sorry, i tend to leave my phone out of my bathroom. not that IP rating is applicable for hot water (or extra chemicals like soap for that matter) anyway.
The focus was "most people," not you. And the iphone's water resistance works just fine in a warm tub. If you're generalizing for what most people need, you should at least understand how people use the devices. Made up constraints like the soap and temperature are irrelevant to common usage and their needs in a device.