Notice the not-so subtle shift in the definition of “shadow inventory” in this article.
The term “shadow inventory” typically refers to homes in various states of foreclosure that would hit the market some point in the future.
This article also includes as “shadow inventory” future inventory from would-be sellers who are not putting their home up because prices are too low.
i.e. those that would put their house up if prices were higher.
This is not shadow inventory. It is simply an example of price elasticity of supply. In this example the supply could be highly elastic.