Aluminium boards, not frames
Aluminium decking means boards made of aluminium, the surface you walk on. Aluminium deck frames are the structure underneath; see aluminium deck frames.
A verified example
DECO’s DecoDeck boards come in two profiles, 94 × 25 mm and 134 × 25 mm, in 6.5 m lengths with a 6 mm gap. DECO describes them as non-combustible under the NCC and says they can be used in bushfire-prone areas up to BAL-FZ, using cover strips for BAL-40 and BAL-FZ. It quotes a P4/R11 slip rating.
These are DECO’s own claims; ask for the test documents before relying on them for a bushfire-prone site.