I think it's because Samsung is trying to protect the screen. I'm curious to see how the Mate X will perform. I won't be surprised if the screen wrapping around the outside turns out to be really fragile. People are notoriously hard on their phones (especially on the edges) and the Mate X is a phone that has an exposed screen that can't be covered in glass and can't be hidden in a screen case.
Samsung's approach has a better chance of succeeding in the long run simply because it protects the screen, but they clearly need to refine their approach. Without some serious materials wizardry, Huawei's design seems hopelessly flawed. According to this article, uneven pressure may be responsible for breaking the Samsung, think of what could happen with the exposed screen on the Huawei.