The Backlights for LCD displays are white LEDs, which are made by using a Blue LED together with a yellow phosphor to transform some of the light for the Red and Green primaries. The spectrum of an LCD display is just the spectrum of its white LED Backlight filtered through the individual Red, Green and Blue sub-pixel filters within the LCD panel.
The LCD RGB spectra are a broader filtered broadband spectrum from the White LEDs, which results in less saturated colors. When more saturated colors are desired, the LCD light output decreases, which then requires more power for the Backlight LEDs.
The Spectra for the Full HD Smartphones are all quite similar as expected. The relative heights of the Red and Green Primaries are due to their different White Point Color Temperatures. Since the Huawei Ascend D2 has a user adjustable White Point, the spectrum shown is for the middle of its range, making it somewhat bluer than the other displays, so its Red and Green Primaries are smaller.