Some soy products are fermented, like tempeh, natto, and some traditionally fermented soy sauce and tamari.
The Whole Life Challenge makes a soy exception for traditionally fermented tamari for two reasons. One is that it is wheat free. Soy sauce is not a gluten free product and wouldn't be allowed at the lifestyle level even if fermented.
Fermenting soy releases an enzyme that then reduces its phytate content and other "anti-nutrients." The phytates contained in soy prevent you from absorbing nutrients in foods as well as inhibiting digestion of the carbohydrates and protein in soybeans.