Lumens mean about as much as watts do to the plant...which is very little, the only thing the plant cares about is spectrum and intensity. I'm with you on that one, there's alot of things growers refer to that really don't make that much sense...everyone gives you their lights in watts per square foot, doesn't make much sense to me, I live in three dimension...height plays a big factor with lights. Also alot of people refer to their PPMs as the number they take off their meters, that is a total PPM, it doesn't tell you what specific nutrients/chemicals make up that amount. I know if you have reliable ferts there is no need to really dive into it, but some plants like different nutes...my WhiteWidow for example loved Mg.