Result number for Boolean queries with Apache Lucene - elasticsearch

Question

When benchmarking Apache Lucene v7.5 I noticed a strange behavior:
I indexed the English Wikipedia dump (5,677,776 docs) using Lucene with the SimpleAnalyzer (No stopwords, no stemming)
Then I searched the index with the following queries:
the totalHits=5,382,873
who totalHits=1,687,254
the who totalHits=5,411,305
"the who" totalHits=8,827
The result number for the Boolean query the who is both larger than the result number for the single term the and the result number for the single term who, when it should be smaller than both.
Is there an explanation for that?
Code snippet:
analyzer = new SimpleAnalyzer();
MultiFieldQueryParser parser = new MultiFieldQueryParser(new String[]{"title", "content","domain","url"},analyzer);
// Parse
Query q = parser.parse(querystr);
// top-10 results
int hitsPerPage = 10;
IndexReader indexReader = DirectoryReader.open(index);
IndexSearcher searcher = new IndexSearcher(indexReader);
// Ranker
TopScoreDocCollector collector = TopScoreDocCollector.create(hitsPerPage);
// Search
searcher.search(q, collector);
// Retrieve the top-10 documents
TopDocs topDocs=collector.topDocs();
ScoreDoc[] hits = topDocs.scoreDocs;
totalHits=topDocs.totalHits;
System.out.println("query: "+querystr + " " + hits.length+" "+String.format("%,d",totalHits));

Answer 1

The explanation is that the default operator is OR and not AND as you assume. Searching for the who returns documents that have either the or who or both.
the - 5,382,873
who - 1,687,254
the OR who - 5,411,305
I.e. most documents that contain who also contains the, except for 28 432 documents which are added to the result set when you retrieve both.
You can change this behavior by changing the default operator:
parser.setDefaultOperator(QueryParserBase.AND_OPERATOR)