not true depends on thow many watts your using in your room. i have produced good buds more than 3 feet from a bulb... at that rate i woud be getting just a couple plants. i filled a 10X20 room with 2 1k lights and 2 600w and a few led pannels lights and it worked great there were entire plants more than 3 feet from a bulb
add the distance between the bulb and the plant for safety, didn't think I needed to add that as it should have been implied, but for pandora sometimes you need to be specific. And yes with many light sources the light intensity goes up as does the overlap coverage.
Keep in mind that at the distance of more than 3 feet (3.6 if 400 watt, 4ft for 600 watt, 5.5 ft from 1000 watt) the inverse square law says the light might be bright but the energy, lumens, intensity has fallen to almost unusable to produce anything but larf indoors.
To help understand, look at this reptile light uvb intensity meter and the distance from the source of light energy.
Best example showing inverse square law and light intensity at different distances. Inside this is what your plants see as light energy from your lights, ie their food and ability to use said light in photosynthesis. Also remember this is not about if you can grow buds far from the light source, it is a question of what quality will said branches produce per square foot and that yields quality at said distance.
Nobody wants to trim larf if they could instead trim weight.\
It's the space between.