Development of doctrine means the elaboration and the detailed application to specific circumstances of the truths of the deposit of faith given by Christ to the apostles and taught in the Church by the apostles' successors down through the centuries in Scripture and Tradition. There can be no reversal of truths forming part of the deposit of faith, whether general concepts on faith and morals that have always been taught in the Church, or specifically defined dogmas with fixed words set forth by ecumenical councils or popes speaking ex cathedra. What can change are disciplinary matters and teachings that are not part of the deposit of faith. At least that is my nutshell understanding of the matter having studied the documents of Vatican I and II and Cardinal Newman on the development of doctrine.
I would agree that the Development of Doctrine only refers to the nature in which it is taught (Theology of the Body as an example). I have no idea where the person who responded to me came up with V2 as changing theology.