So keeping long story short is that you have no way of proving that your device wasn't deeper than 1.5 meters for up to 30 minutes. Inside the S7 there are couple moisture stickers. One is near a sim tray and one is on the speaker. They will pop the tray out look at the sticker to see if it's purple and if it is they will assume it wasn't used according to specification. There is no other way to prove you didn't misuse it.
Also, while the buttons and SIM tray are protected by gaskets and seals, remember that over time these can wear or get damaged by dirt and debris, which in turn can dramatically reduce the water resistance of the device.
The lack of a water repellant coating on the circuit boards, along with the moisture-detecting stickers, is also worrying to me. If water gets inside the device, then the consequences (all of which are bad) of that are all your problem.
So in the end you are playing with a bunch of what ifs and should haves, would haves and could haves.
Also no one will follow THESE, because no one will bother to look it up. So yeah it's a GIMMICK.