Confusing documentation on Parallel builds

When I asked someone about parallel builds, I got the following response: In general you should be able to get a parallel executed build for a project with three subprojects as you have described. I pushed a sample skeleton project setup at https://github.com/breskeby/gradle-snippets/tree/master/multiparallel

But in the Gradle manual: gradle.org/docs/current/userguide/multi_project_builds.html

It says: “coupling of projects effectively prevents Gradle from building multiple projects in parallel”

and

“A very common way for projects to be coupled is by using configuration injection. It may not be immediately apparent, but using key Gradle features like the allprojects and subprojects keywords automatically cause your projects to be coupled.”

Sorry, the URL was reformatted, the correct link to the manual is here.

It’s not clear what your specific question/point is.

The definition of decoupled projects is not clear . If I use “allprojects” ( though the projects are actually independant ) in the configuration , then does it imply projects are coupled ?