If you use open-source software, you might wonder, why all those changes and why you should migrate up to the next major versions. Some don’t even (properly) migrate the minor version of the framework dependency to the latest available release…
This 4 year old post already blogged about it. Surprisingly many libraries still don’t use it in their CI system yet. The –prefer-lowest option has been added around that time. Composer documentation says: "Useful for testing minimal versions of requirements"….