Unless I misread J.D's article there's a point I disagree with. For obstacle clearance he seems to be advocating that - given more runway than the ground roll requires - the a/c be kept on the ground until some speed higher than Vx (or maybe accelerated after lift-off to some speed >Vx) THEN the a/c is zoom climbed, trading speed for height.
If that's the case then there's an error in his method: Any speed greater than Vx is wasteful of energy due to the greater proportion of drag reducing the excess available for climb. Think of the power & thrust required/available curves.
Have I misread something in his article? Or am reading more into it than he intended?