No, it is not "a fact". It's a marketing ploy.
You don't understand lumens. Your eyes need even lighting, and not too much directly pointed at you, regardless of what you are doing. People give themselves headaches (or at least get over-tired) by looking at things with uneven lighting, it causes strain. TVs, computer screens, books, etc. It doesn't matter if the ambient is too bright or too dim, both can cause this. Most people are probably reading more often in ambient light close to what they need for books, and I suppose e-ink. Doing it properly more often does not mean the product is better, it means people are idiots as soon as they use something else.
TVs and computer screens and iPod/PDA/smartphone screens are set too bright by almost everybody. It's insane. I tell people about this all the time, 99% don't listen. Like you.
Cnet actually reviews TVs claiming they should give a 40+ ftL lumen output, based on ambient light. Funny, the experts that actually create TV and movie tech standards at THX and SMPTE claim it should be 17 ftL.
I can read on my Touch for hours with no headaches. I can watch the entire Lord of the Rings trilogy in one day with no headaches. Proper settings. Couldn't do this before I learned about it.
and I swear I'm not picking on anyone