1.) Wired sure does love yellow light! Kinda odd, since this is a magazine that is, ostensibly, about modern technology; unlike say, Good Old Days.[1] What they smoothly elide is that the sensitivity of the human eye peaks at 555 nanometers. (green)[2]
The more red you have in your white light spectrum, the less efficient the lamp is.
This is a hard physical limit. No amount of cleverness will get around it-- the eye just isn't as sensitive to red light. The warmer the light, the less efficient your bulb will be. 2700K (warm-white) is pretty bad. 5500K (pure white) is okay. 7000K would be ideal, but I don't think anybody actually makes lamps with a color temperature[3] that high.
2.)
...Additional colors and increased brightness required more nuanced control
of layer composition and depth. Modern LED makers accomplish this by using
precise ratios of indium, gallium, aluminum, and nitrogen for the crystal
layer, which results in a bluish color.
But on their own, not even advanced LEDs can produce anything suitable for
the living room. The blue-tinged illumination is fine for, say, a pen
flashlight on a keychain, but it doesn’t come close to the warm light the
human eye desires.
So the LEDs found in current household applications are blue diodes daubed
with a powdered coating called a phosphor, which includes rare-earth
elements that filter blue light.
---
1: Actual magazine, that actually exists. http://www.goodolddaysmagazine.com/
2: https://secure.wikimedia.org/wikipedia/en/wiki/Luminous_effi...
3: https://secure.wikimedia.org/wikipedia/en/wiki/Color_tempera...