I'm an aerospace engineer and I have designed and run plenty of tests for certification of aircraft parts. This test is fine as far as it goes but it is
not testing the real issue, the FAA would have thrown me out of the room if I'd shown them this.
What the test shows is that most phones will resist a reasonable amount of bending when the load is applied uniformly at the centre. They all do pretty well. That's great.
The issue with the iPhone 6 Plus is that it has a weak corner, if you watch the 'bendgate' video you can clearly see that the bend line is not straight across the phone, but at an angle near to the weak spot.
A properly designed test would have clamped each phone flat with a corner sticking out unsupported and force applied until it suffered plastic deformation (stays bent). Each phone could have all four corners tested and the weakest result is the 'winner'. In such a test the iPhone 6 Plus would clearly fail at its weak point much more readily than any of the others.
Bad science.