Well, otherwise there's more than one salt (and the so-called salt substitute
is potassium chloride, but it isn't merely a flavor substitute)...
Dietary potassium deficiency, common in Western diets, raises blood pressure and enhances salt sensitivity
Compared to diets consumed by our evolutionary ancestors, the majority of people in the world today consume a diet relatively high in salt (NaCl) and low in potassium (K+). A high dietary sodium (Na+) to K+ ratio is associated with hypertension, cardiovascular disease, and all-cause mortality.—Potassium Modulates Electrolyte Balance and Blood Pressure
The Cardiovascular Benefit of a K+-Rich Diet Is a Gift From Our Past
Early terrestrial animals, like hunter-gather groups, consumed diets with high K+ and very low Na+. To maintain extracellular fluid, animals evolved salt-retaining genes, including genes for salty food preference; once salt was commercialized by humans, salt-seeking behaviors drove very high NaCl consumption. Consequently, although our human physiology has been fine-tuned to handle high-K+, low-Na+ diets, typical Western diets contain far less K+ than Na+.—Potassium Homeostasis: The Knowns, the Unknowns, and the Health Benefits
Supposedly if people (without a risk of hyperkalemia due to existing health conditions) would eat at least as much salt substitute
as they did salt, it would be a more balanced diet then. Maybe this explains to some extent why the first article had inconsistent data about the effects of sodium intake alone (because it also depends on potassium intake). That said, it isn't something to get carried away with either, as the lethal dose of potassium
is lower than that of sodium.