Some were, some were not.
If you share interiors, drivetrains and options then it's a rebadge. (Fusion/Milan, CV/GM, Ranger/B series, Explorer/Navajo)
If you have unique drivetrains, interiors and options then it's platform sharing which then breaks down into 2 categories depending on whether they share sheetmetal/greenhouses (like the Fusion and MKZ) or not (like Flex, MKT and Explorer).