It seems that the way tooling is putting multiple components into the reference promotion attribute (separated by space) does confuses the V1CompositeReferenceModel.getComponentReference() method and outputs this warning:
[org.switchyard.config.model.composite.v1.V1CompositeReferenceModel] (MSC service thread 1-6) missing component reference for component [SomeComponent]

That method only expects to see 1 component in there. If you use multiple separated by space than "String[] promote" will have more than 2 elements and won't be able to resolve the right component