Wouldn't this be exactly what you'd expect given that they are modular? Modular as in flexible and re-usable in different contexts for different purposes?
Why would more uncertainty = bigger cluster? Wouldn't uncertainty be expressed by using smaller clusters? I.e. if you're uncertain about a cluster you fall-back on a smaller subset of things that you are more certain pertain to that classification?
Would you say that brain is a modular system because the environment it's meant to model is modular? E.g. social systems as a collection of modules (humans).