It's always fun when home tent growers think they know everything... And I'm wrong yet no one has definitive proof contradicting anything I've said where's your links boys?
The OP said in his original post its a 252w light. its called a 1200w light because of fuckery, as in its 400x 3w diodes, even though they are run very soft to get 252 real watts they cling on to the title of 1200w because it sounds more impressive to the untrained buyer.
Your right though 50w per square foot is a HID thing, guys with quality LEDs are running 30-35w per square foot with some going a bit less and some going up to 50w per square foot, but most around 30s.
Only shit lights use the diode count X diode max wattage title scam. Good LEDs are called what ever the true wattage is.