The First Order Reversal Curve (FORC) method is widely used for the magnetic characterization of interacting systems, where the resulting diagrams are commonly interpreted as direct representations of intrinsic coercive and interaction field distributions within a Preisach-type framework. However, this interpretation becomes questionable in the presence of magnetic interactions, where collective effects dominate magnetization dynamics. In this work, we present a combined theoretical, numerical, and experimental study demonstrating that FORC diagrams should instead be understood as the result of a differential transformation applied to a path-dependent magnetization response. Using assemblies of magnetic nanowires as a model system, we systematically analyze the influence of intrinsic switching field distributions (iSFD), mean-field interactions, and interaction field dispersion. The results show that key features of FORC diagrams, including broadening, asymmetry, and the emergence of negative regions, arise naturally from interaction-driven modifications of the magnetization curves and their transformation, rather than from intrinsic physical distributions. Simulated diagrams based on experimentally derived iSFD and interaction parameters reproduce the main experimental features, showing strong quantitative agreement. These findings establish an alternative physically consistent framework for interpreting FORC diagrams in interacting systems, emphasizing their nature as differential signatures of collective magnetization dynamics and highlighting the limitations of their use for direct quantitative extraction of intrinsic magnetic parameters.
