This implementation is somewhat special from our other Gradle properties, because it does not get declared in the root gradle.properties. The reason is that included builds are supposed to have their own properties e.g.
root_project/gradle.properties
root_project/buildSrc/gradle.properties
root_project/build-conventions/gradle.properties
Instead of declaring the property in three different places which might lead to confusion, this leaves the property undeclared, with the Gradle scripts assuming a default value of true. The only time this is expected to be overridden is due to a workaround for an Android Studio bug.
Carter Jernigan