I can believe it; in the UK our fire regs have become rather stringent due to the Grenfell fire, though those changes are mostly on flats/buildings more then 3(?) storeis etc.

The PVC external cladding can melt from a mid to large sized bonfire 10-15 foot away. We can't use it to clad houses above the 2nd floor, though there are exceptions if your replacing existing cladding. So if you want to add a former to your loft you have to use tiles now.

Though there's this interesting product called magply which is roughly as strong as ply, but is made from magnesium oxide and silicate. It's considered incombustible so you can clad with it, then render it.

I wonder if we'll start seeing different materials used in areas prone to forest fires