Ya no I get that what would be best for one could be worst for another. Im saying based on his findings which was best placement according to his graphs. Idk how to read those
First, those aren't straight frequency response graphs. The first graph is showing where the peaks and nulls will be, and their magnitude with respect to frequency. The second graph is showing approximately where those peaks and nulls occur in the room (L X W). None of this takes into account furniture etc. Plus all graphs will be slightly different for a room of different dimensions.
The "best" depends on room orientation, room dimensions, and the way the seating is oriented. IMO, based on the room orientation and the graphs given my preference would be with the subs placed at the mid point of the side walls. Like I said, all this is moot, real world unless you're setting up a customized HT room where more variables will be under strict control.