Our Big Hole

So here is our gigantic hole. Do the Pumpkin roots really go down that far? What is the purpose of the 3x4 hole? Ours is more like 2x2 and 1/2ish. We filled it in with a mixture of peat moss, manuer, and good fertilized compost. I am getting a bunny so I will soon have bunny fertilizer.... Here are pics of the Richardson's Big Hole.