If that statement was true, every single nation with a population growing would be developed. We know that is far from true.
Economic development is actually a complicated definition, as it includes "well being" of population and that might differ among economists. It is generally accepted however that Economic development comprehends economic growth, generation of wealth, transitioning from an agricultural economy into an industrial based on knowledge-economy, access to technology, etc.
In developed countries, population growth is less important than having access to education, health care and technology.
In developing countries we observe populations growing but with poor to no access to education and other resources, so poverty multiplies as population grows.
Hope this helps.