Your parent is not talking about organic methods, but rather different varieties of crops. E.g., big red beefsteak tomatoes are popular and travel well while little heirloom varieties do not, so you are going to have access to additional, possibly more nutrative, varieties if you buy local.

This has nothing to do with "organic" anything - the conditions of breeding - but modern breeds of vegetables and fruit. There's no shortage of evidence of the difference, and the decline in vitamin content over the last many decades, in the U.S.