I always understood (from old navy days) that halon needed to be win a fairly confined space to really work effectively - wouldn’t atmospheric dispersion reduce it’s ability to work?
Maybe that was also because there wasn’t a whole lot of halon in a discharge. If that problem could be overcome (large quantities, and maybe a halon-oxygen mix that would avert smothering problems for humans and beasts caught in it) then we’d have something that could be dumped on a large fire to put it out with little or no harm to humans and beasts.