Good point. This seems to be a gray area. Minimum, maximum, ample, optimal... There is the amount of light that will reach a total surface area of the canopy sufficiently to grow evenly, and then there is the additional amount of light you can add to the same area to encourage maximum growth. Sellers tend to want to promote the largest possible footprint, growers seem to want to figure out how much light they can throw down before the plants are over saturated. Somewhere in the middle is probably a sweet spot... but I doubt there is one single right answer, just guidelines and references.