I think extending and unbalancing uke (kuzushi) is needed in every technique. So it is in shiho nage.
But: Is following nage a concept of your aikido also on an advanced level? Or are you talking about beginners only?
I am talking about all levels.. at our dojo, we always practice following... occasionally we do tight grips and practice with resistance, but not to the point where you just stand in one spot (because then you're not doing anything either, then what's the point of nage doing a technique). The reason we practice resistance, and usually with more advanced students, is to teach nage to find a weakness and exploit it. The reason we practice following is so that uke can detect weaknesses in nage's technique and, if it were a real-life situation, perform a counter. The more you follow, the more balanced you are, and the more chances you have to get ahead of nage.