I'm of the opinion that stuff like f.lux and Apple's Night Shift are both products that exploit pseudoscience to take advantage of the placebo effect. They're a "gluten free" feature for contemporary software — for those suspicious of childhood vaccinations.
Macworld wrote a decent breakdown of the Night Shift quackery when it was introduced:
http://www.macworld.com/article/3047121/iphone-ipad/ios-93-t...