If any phone is going to be subject to the same force at the edges, regardless of length, then that's what you want to be measuring. It doesn't matter if a long

If any phone is going to be subject to the same force at the edges, regardless of length, then that's what you want to be measuring. It doesn't matter if a long phone can handle slightly more torque than a short one, if it's going to be subject to a lot more torque. I don't know what the stresses applied to a phone in a pocket actually look like, but it's not obvious to me that measuring force rather than torque is unfair.