Depriving the fire of oxygen accomplishes everything that Halon
can.
Not true, not true at all. Halon works by not only starving the fire of oxygen, but reacting with the radicals that propogate the fire. All halogenated extinguishers work this way.
You can put out an self-oxidising fire with Halon, you can't by putting it in an inert atmosphere.
We have three different extinguishers in our labs for very good reasons, they all do a different job, on different reactions.