ok here is my opinion on the matter. the lights are shining on an area. In order maximize the amount of light in a given area we add more bulbs. Example: a 5'x5' grow room. lets say you have one bulb that puts out 10,000 lumens. that bulb, depending on size and reflector, can only cover so much of that 5'x5' area so we add 3 more of same bulb. Now, we dont have 40,000 lumens hitting every area of the 5'x5', nut the total lumens are 40,000. 10,000 in every fourth of the area. now vertically, lumens are affected as well. Example. at a foot you receive the 10,000 lumens but with the light 2 feet away you receive 4,500 lumen. everything i am writing is my belief on the situation. The numbers are just made up not exact and not pertaining to one specific bulb. just a guideline. So all in all, the thread starter and you growers are right. +rep me if this makes sense.
Ed Rosenthal is a great person to learn from Read the Marijuana growers handbook. you should read up. Also to the thread starter, you should really try growing or at least referencing the things that you are saying. people will accept your opinions more.