Many times, this is due to lack of communication. The inspector may not be aware that you will be using a "floating system" or may be assuming that you'll be attaching the deck to the house. It is extremely odd for a local building code to "require frost footings for all decks." Typically frost footings are required if the deck is attached to a fixed object, similar to a house. The Floating Foundation Deck System is a different building method. Print out the plans you will be using and the technical reports from the building code section when presenting to the building department/inspector.