One of the metaphors I use when I talk why a kanban system has work-in-progress (WIP) limits, is traffic jams. The greater the WIP, the lower the throughput, and this effect can be seen when too many cars clog up a motorway. Watching the BBC’s “Britain from Above” last night, they had an interesting section on this subject, including a nice simulation on how a bottleneck ripples back as it frees up, explaining how traffic jams can seem to appear and disappear for now apparent reason.
You can seen the clip here – the simulation is about 3 minutes in.
I expect you get the same effect in software development value streams, although I would also expect that software development value streams are short enough for the effect to be unnoticeable.