ecm:parentId is not populated in mongodb for versions. However it is in the Elasticsearch index.
The following query returns nothing with a core pageprovider while it returns all the versions present in the folder with ES.
It feels like an exact match query on system properties should return the same results with both types of pp (assuming the ES index is up-to-date).
The current behavior of the ES pageprovider provides more query possibilities on versions than the core pp