Hello pleco...
You may be right. No doubt the use of standard aquarium salt is a personal choice. My belief is tropical fish all come from water areas that have a natural salt content, so my job is to keep the tank environment as close to nature as humanly possible. Water passes through a fish's gills more easily with a trace of dissolved salts in the water and benefits their immune system.
I keep several varieties of Corydoras, fish that are also sensative to salt and have never had a problem.
When I started my tanks several years ago, a friend who'd been a fishkeeper for many years, encourage me to use a little aquarium salt in my tanks, because he believed it killed disease causing bacteria he said were present in all tanks. That was six years ago, and I've never had a disease in any of my tanks.
"An Ounce of Prevention is Worth a Pound of Cure."
Thanks for your post.
B