But isn't Randori ( and all of Aikido) simply folks running at you( mostly one at a time) with the intention of you throwing them? It's preplanned and they fully cooperate ( dang near throwing themselves). Imo, Randori should be called multiple fully cooperative ukes. On the street, multiple attackers means a real real bad situation.
Randori of this type is designed to teach you how to move on the outside of uke, to tenkan, to triangulate, and to disrupt the tempo. I think it really has very little to do with self defense directly. It is a very, very basic exercise. Mainly for as the reasons you state, nage knows your coming, uke must "bail" at point of impact, and it is cooperative.
Not a bad exercise for what it is, but I think many people read into what it really does for you way too much.