Sodium in isolation might cause high blood pressure in certain people depending on the proportion of water and other electrolytes in their diet. Your body excretes water, sodium, and other electrolytes in proportion to maintain osmotic pressure within the cell and in the intracellular spaces. This is handled by the kidneys.
If you over-consume any one electrolyte or water compared to a baseline osmotic pressure may increase or decrease until the body compensates. This is from the article.
I'm not a doctor but I've taken some first aid classes where electrolyte and dehydration were covered in the context of hiking and backpacking. It's also possible to drain your body of electrolytes by sweating, because again the electrolytes must be present in proportion to the water and sweat contains electrolyte because the glands need the proper osmotic pressure to induct water. You may also drain electrolyte into your intestine because the body also needs the water to have the proper osmotic pressure to absorb it in the first place. This is why Oral Rehydration Salts have table and other salts in them.
The body is extremely complicated, and I'm always very suspicious when someone tells me that "X causes X" without explaining the mechanism of action or the caveats. Every body is different and the same body in different situations will require different treatments. Complex dynamical systems frequently exhibit chaotic behavior. Chaotic systems have the feature that taking the same intervention and applying it at slightly different points in the system's evolution can produce wildly different sequences of further evolution.
I hope that one day nutritional science will have advanced to the point where this is understood and expected during study design. But until that happens it's hard for me to believe many nutritional studies.