Confused by DiversifyingChildrenFloatKnnVectorQuery javadocs

I believe I understand the *purpose* of the 
DiversifyingChildrenFloatKnnVectorQuery (and 
DiversifyingChildrenByteKnnVectorQuery) classes, but what I don't 
understand is the java code example from the javadocs...

https://lucene.apache.org/core/9_12_0/join/org/apache/lucene/search/join/DiversifyingChildrenFloatKnnVectorQuery.html

Query knnQuery = new DiversifyingChildrenFloatKnnVectorQuery(fieldName, queryVector, ...);
// Rewrite executes kNN search and collects nearest children docIds and their scores
Query rewrittenKnnQuery = searcher.rewrite(knnQuery);
// Join the scored children docs with their parents and score the parents
Query childrenToParents = new ToParentBlockJoinQuery(rewrittenKnnQuery, parentsFilter, ScoreMode.MAX);

...why does this example suggest that the "caller" needs to call 
searcher.rewrite(knnQuery) directly and then pass the result to the 
ToParentBlockJoinQuery constructor?  Isn't that rewrite going to happen 
automatically when ToParentBlockJoinQuery.rewrite() is ultimately called?


Also, FWIW, I can't sem to find any tests this particular 
method of combining DiversifyingChildrenFloatKnnVectorQuery with 
ToParentBlockJoinQuery produces expected results -- making me suspicios 
that it's not actaully neccessary for correct behavior?

(Allthough, for that matter, I'm not seeing any tests that actual involve 
wrapping DiversifyingChildrenFloatKnnVectorQuery in a 
ToParentBlockJoinQuery -- only lower level "white box" style tests that 
assert DiversifyingChildrenFloatKnnVectorQuery returns the expected 
diverse matches)



-Hoss
http://www.lucidworks.com/