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A ballasted keel provides lateral resistance, which tends to prevent the boat from side-slipping when it's sailing to windward, and it provides a weighted lever, which resists heeling. There are all kinds of swing keel and centerboard configurations. Some designs use a swing keel that retracts snugly up against the boat's bottom, like a CATALINA 22 OR 25. When that type of keel is retracted, it greatly reduces the keel's effect as ballast (to resist heeling), but the retracted keel still provides a great deal of lateral resistance. When that type of keel is fully retracted, the same amount of surface area is still submerged in the water, and it still provides nearly the same amount of lateral resistance. IOW, Retracting this type of keel doesn't significantly reduce it's lateral resistance.
By comparison, some boats carry their ballast in a centerboard trunk, which can't be moved. They often have a centerboard or daggerboard that swings or is raised up into the centerboard trunk. If the entire surface of the centerboard is retracted into the centerboard trunk, so that the water is no longer flowing across the surface area of the centerboard, then retracting this type of keel significantly reduces it's lateral resistance. Of course, the centerboard trunk itself provides lateral resistance, but, to the extent that the centerboard surface is retracted into the trunk, the amount of lateral resistance is reduced.
So, the effect of raising or lowering a swing keel depends very much on how it's designed.