I think you meant it grows as the square of the blade length (and the cube of the wind speed)

From your link: > Thus, the power passing through the blades of the turbine, and thus in turn the power of the electricity the turbine generates, is proportional to the square of the length of the blades: a doubling of blade length leads to a quadrupling of wind power passing over the blades.

Doesn’t change your conclusion of course. Thanks for the interesting link!