Why is the formula for prostate volume pi/6*(length*width*height) and not 4/3*pi*(length*width*height)?

Multiple sources state that the "prolate ellipsoid volume equation" is used (example 1 2 3).

The formula is listed as: V = (π/6)lwh

Wikipedia and Wolfram list the formula as V = (4π/3)lwh

This makes more sense due to the fact that it would reduce to the volume of a sphere if lwh = r^3 and is the result you would get from integrating the ellipsoid equation.