Maybe when saying something like that it would be good to explain why.
...And maybe Byron could repeat his relatively unpopular theory as to why it is?
I know he favours a particular piece of science and implies that everyone else is wrong because of this.
Essentially, natural fresh water, the environment in which fish reside, contains all manner of minerals/electrolytes, etc. and these are necessary for fish health.
Besides facilitating good immune systems, it also works against bacteria and fungal organisms.
Tap water has many of these removed and, when you throw in water conditioners, etc., the water we expect our fish to thrive in is relatively sterile, lacking those essential minerals and electrolytes.
Basic Aquarium Salt addresses this issue without having to carefully contact a mix of minerals.
This very basic concept is supported by all of the knowledgeable aquarists and fishkeepers I'm familiar with on YouTube.
Problems arise when people throw in basic table salt, or other salt that hasn't been recommended for aquarium use, which contains harmful (to fish) additives, such as extra minerals or anti-clogging/clumping agents.
Problems also arise when people overdose the stuff...as with anything that you can add to a tank.
In a relatively low dose, it'll maintain a basic, healthy level. At a slightly increased dose, it'll destroy fungi and bacteria and other pathogenic organisms.