At the beginning, maintaining the required volume is significant. It forces you to listen to your body to manage enough rest between sets. Plus, even there is a significant volume, it is not "that much". I mean there is no risk of overtraining with S&S if you do it on a stand alone and if you do not do anything else simultaneously. This volume builds a very strong work capacity.
Waving can be interested when you want to mix S&S with other activites or if you want to target some special aspects such as long endurance (more than 100) or heavy weights (sometimes less than 100 to maintain perfect form). Waving can be a good idea to focus or break a plateau.