The answer to this is fairly simple.
Yes the jar becomes available to :app, but it must be listed as a dependency in :shinobicharts-android-library
The tutorial I followed gave the incorrect version of the jar.
Note the subtle difference between (shinobicharts-android-library/build.gradle)
dependencies {
compile files('libs/shinobicharts-android-trial-1.2.0.jar')
compile files("$buildDir/native-libs/native-libs.jar")
}
and
dependencies {
compile files('libs/shinobicharts-android-trial-1.3.2.jar')
compile files("$buildDir/native-libs/native-libs.jar")
}