All ions drop with the salinity correction, and my part 3 only deals with magnesium and chloride and sulfate issues.
Sodium is dealt with by the salinity correction.
My original recipe also solved it for potassium since it was an impurity in the calcium chloride (Dowflake) at the right level). But higher purity calcium chloride may not have sufficient potassium, so it and a variety of minor and trace elements may decline, while they would not using Balling Part C instead of my DIY part 3.
As to the impact of water changes, they reduce the concern. they may not eliminate it.
IMO, this issue is not very significant for consumed trace elements, but is most important for potassium and the minor ions that are not otherwise consumed much. The actual consumption and loss of ions like manganese and iron is far higher than any lowering from salinity corrections. hence the need for supplements, even when changing water.