Yes, i'm talking about someone who knows his beans and has his grow setup perfectly. Is that not how all advertising works, if we are working on the premise that the advert is accurate in that 1 in a 1000 scenario. Just as a car company will advertise a 0-60mph time as a selling point, but most people should be fully aware that without lots of experience, actually hitting that advertised time is not very viable straight off the bat until you understand what revs you want to be changing at, what revs to be at when you leave the line, how fast to raise the clutch etc.
Also, with regard to even uptake and such, it could be swings and roundabouts, doesn't have to be even. Some plants could only yield you 20 grams, others could yield 40 grams. Just saying that an ounce in a 6" square footprint is not by any means impossible. It is reproducing that kind of result across every strain that will require the experience.
Also worth baring in mind though, that the advertised 900g/m square is not saying that buy a light and a meter square tent and you will get this, they could have a room with 9 1kw lights, and right in the middle of the room where it's like the sun itself, they could find that number, despite on the outer edges of the room, that figure dropping.
