Are dependencies of a source dependency pulled in transitively?

Introducing source dependencies

This article fails to address a crucial point, which is, whether dependencies of the source dependency are pulled in transitively. Can someone answer that please?

Well, it addresses it implicitly.

The post says “Source dependencies are based on Gradle’s composite build feature and add automatic provisioning of the source code”.
So, what is true for composite build is also true for source dependencies, so yes.