You are right, of course, however, I have built quite elaborate LED-based backlight systems and have metrics on this too. A few years ago we did a custom system with a 1,000 Watt (yes, one thousand) custom liquid-cooled RGB LED backlight. Performance depends on many things, from aperture ratios to the spectral transmission characteristics of the filters as well as how they match the emission spectra of the backlight elements.

With regards to getting in touch, email me at martin_05 the domain is rocketmail and TLD is .com