It doesn't really work that way. Harder, cold worked brass is more stiff and brittle so it obturates (forms around) the mandrel more and doesn't spring back as much as softer, annealed brass. Think of metal fatigue, if you bend it enough times without heat it will eventually stretch out and break.
If your theory is correct annealing the brass so it is very soft would give more neck tension. To carry it to an extreme if the brass is dead soft obviously you would have very little neck tension. The purpose of annealing is to get consistent tension. Annealed and unannealed brass would both be in elastic tension. If both conditions had the same amount of spring back. I would think the harder brass would pull back with more force.
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