Calling KmlLayer::getContainers() returns null when calling it prior to adding the layer to the map by calling KmlLayer::addLayerToMap(). This makes it impossible to retrieve containers (and nested data) without adding the layer to the map first, and also causes KmlLayer::hasContainers() to fail with a NullPointerException.
The cause is that KmlRenderer::mContainers is only set during addLayerToMap (and retains its initial null value until that point).
A current workaround seems to call addLayerToMap() followed by removeLayerFromMap() though this is far from ideal.