The slower rate means you need less time to break reducing the distance you need between cars and increasing capacity of the road and the constant speed reduces the break/acceleration cycle that is needed to sustain the wave.
Then of course other jams are caused by inefficiencies in merging which ripple out to all the lanes as people try to get out of the lane that is going to merge. Self-driving cars of course would have the advantage here since they would no doubt be able to merge at higher speeds.
Traffic jams caused by accidents would hopefully be reduced if self-driving cars get into fewer accidents.
And finally, it is conceivable that if you are in a lane full of self-driving cars - especially ones that communicate between themselves - and if it is shown conclusively that they could cope faster in case of a catastrophic event, you could allow them to drive faster the speed limit.