The glass on the iPhone are NOT confined, it is allowed room to expand. If you look at how the iPhone glass is mated to the phone, it sits on top of the aluminum case, and there is a thin elastomer gasket between the lower-edge of the aluminum frame and the glass section that "snaps" into this. The aluminum frame will flex, to allow for expansion - and the elastomer helps maintain a water-tight seal. You only need a few thousands of an inch of space for thermal expansion. The linear coefficient of Glass is 3.3 (10-6 in/(in R)), Where R is the temperature in Kelvin (F). So, if you take the glass from the summertime high of 100F to a winter low of -20F, you have a delta of 120F x (3.3x10^-6), or allow for a glass expansion of 0.000396 inches for every linear inch of screen (in X and then the Y axis). Ideally, you would calculate something in the middle temperature range as your norm, so your deviation would be about half that. The math isn't that hard.

Huawei opted to capture and hold the glass in a frame that doesn't allow for thermal expansion. Obviously, this is a problem.