A water softener does not make water salty. A water softener does not add salt to your water. The salt is used only to regenerate the resin beads (at set intervals) so that these resin beads can later be used in the ion exchange process to soften the water as the water is used at end points (faucets, dishwasher, washing machine, etc). When the salt brine solution is made during the regeneration process the last step is to fully rinse all the remaining salt out (the salt that remains that didn't give up ions to the beads) . The softening process when consuming water at end points replaces calcium and magnesium ions for sodium ions by these beads. The beads now full of just sodium ions (when freshly regenerate) get swapped out so that the calcium and magnesium are the ones that end up stuck to the breads as the beads give up the sodium. Sodium is not salt. Sodium is only half of what makes up salt, as salt is sodium chloride (NaCl). Since there is no chloride, there is no salt in your water. Yes the salt is the source of the sodium, but realize that you lost the other half of what constitutes salt during the process. People with high blood pressure or other heath concerns are told to limit salt intake not because of the entire salt molecules but rather just because of the sodium part of what is salt. Therefore these people have the same concern with water softeners as they are putting in sodium into the water. But there is an alternative for these people to soften the water a different way, as they can use Potassium Chloride instead of salt. The potassium ion is then used in the system instead of the sodium ion and it works but isn't as efficient as sodium chloride (salt).
Regardless, hard water with calcium and magnesium versus soft water with sodium (or potassium) is not adequate for any scientific purpose. Destiled water or reverse osmosis water would yield better results.