When article is created using CX, it is expanded in many bigger languages than original article itself. There is good opportunity to expand original article here. Notifying article creator is the one way to do it.
Currently, when article is created using CX, if subscribed Wikidata will send notification of addition of link to article created in a new language. Example: https://www.wikidata.org/w/index.php?title=Q28858561&diff=next&oldid=458644048