This is too general a blanket statement to be true. Plenty of wood in construction is not treated for fire. Fire ratings are generally done for assemblies, not

This is too general a blanket statement to be true. Plenty of wood in construction is not treated for fire. Fire ratings are generally done for assemblies, not components of assemblies, and there are ways to build fire rated assemblies without treated wood. Also, not all assemblies need fire ratings. Sometimes its just the exterior walls adjacent to neighbouring structures, etc.