True, but they are relatively easy to replace, if needed.
For those of us with granite tap water (foul tasting, high sediment ground water with a GH of 27-30...) not using a water softener for the sake of the home is insane. The lime deposits on fixtures, appliances, etc. simply make it impossible.
You don't necessarily need to explore bypass if you can use K salt. Other challenges can be overcome.
But if your growing plants, the bypassed water is far better, and you wont need to worry about adding calcium and magnesium back or purchasing it either, plus after all is said and done, the water will have a higher TDS and sodium content than it ever did originally.
I would think finding the bypassed tap would be the easier solution, than getting the parents to switch to a different brand/type of salt.