I wouldn't be surprised to see that this study is never reproduced.
Another guess: they might actually find similar retinal problems from sunlight exposure in people who spend most of their working life outdoors, but since most people in developed nations don't work in agriculture anymore their baseline population doesn't reflect a lot of sunlight exposure.
(IIRC blue and violet LEDs are close to 100% efficient, but our eyes are much more sensitive as the wavelength gets farther from violet. This means that the "efficacy" of less violet LEDs is much higher. The backlight power will be set to achieve some desired apparent brightness, so a longer-wavelength blue primary would save power.)