Thank you everyone for the feedback! I've implemented and committed the flatter structure: https://issues.apache.org/jira/browse/SOLR-7422 So either form can now be used (and I'll be switching to the flatter method for examples when it actually reduces the levels).
For those who want to try it out, I just made a 5.2-dev snapshot: https://github.com/yonik/lucene-solr/releases -Yonik
