Yes, I was taught the same thing. I'm ready to stand corrected, but I think you'll find that that relates more to a full rated climb versus a reduced rate climb (to cruise altitude).
It's a very different matter if you're including the takeoff power setting into consideration, particularly on an engine the size of the GE-115B. Take a look at the difference in fuel flow on a TOGA takeoff versus a 72 or even 45 to 50 degree assumed temp takeoff. It's considerable.
But as I said, I stand ready to be corrected by people far more tech savvy than I'll ever be.