There is no problem complying with BCA fire requirements since single-storey Type C buildings do not need any specific FRL if 3.0m or more from a fire source feature (Table S5C24a). Clause F3D5 in Volume 1 is aimed at waterproofing and, as you say, does not include timber cladding as a Deemed to Satisfy solution. Currently, a Performance Solution would be required.

Tongue and groove flooring was often installed on verandah floors in earlier times but is not generally recommended today. Timber decking is installed with spaces between the boards to allow for swelling and shrinking in responses to changes in moisture content. Flooring is kiln-dried to a moisture content suitable for interior use, and is likely to swell if exposed to rain or high humidity outdoors.