There is a big difference between Naturally brewed and commercial soysauces.
A naturally brewed soysauce usually ferments for a period not less than six months, and up to a period of two years.

Our soysauce ferments for two years in open cedars vats with out any processing additives.
A commercial soysauce will ferment for as little as six weeks and will contain many additives like colouring, sugars and preservatives.

Nutritionally, and flavour wise, they are worlds apart.

High quality shoyu and tamari have an excellent bouquet, and a broad culinary use.

Shoyu: Is made using wheat + soybeans + seasalt + koji extract. Shoyu is the most commonly used soysauce in Japan. It is an excellent flavour enhancer.

Tamari is a "wheat -free " product, a little fuller in flavour than shoyu and darker colour.
They both share a similar nutritional profile and seem to be more popular in the west.

Many sauces are made in such a way to speed up processing. What this means is that a soy "mash" will be used instead of whole soybeans.

This "mash" may then be treated with an acid to break it down. Requiring further treatment with a solution.

It will also need some colour (caramel) and preservatives. Resulting in a dark salty fluid. A traditional sauce uses whole soybeans, and is allowed to fully ferment,
So the beans naturally break down over time, This results in a full flavour and versatile addition to any meal.