This article presents an accurate study about the validity of the tuning rule for symmetric-send-on-delta (SSOD) based PID controllers which was presented by the authors in a previous work. First we obtain the conditions under which the rule is valid and then we study its fulfillment for an extensive batch of 134 models. The results demonstrated that most of the models used in practical applications fulfill the validity conditions, and consequently the rule can be useful for tuning SSOD based PID for a wide range of systems.