All the files may not be deleted off simulator or in the case of a development build on device. This has something to do with Xcode not wanting to have to reinstall the entire app bundle from scratch every time it builds during development. Instead of trashing everything, it just alters what was changed.
This can cause problem e.g. . Xcdatamodel files don't seem to be reliably removed from the simulator when the file is removed from the build target.
Deleting an app deletes its sandbox. That includes core data files.
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