Per Lucene documentation, the following is definition of Indexing Rules on oak indexes inside AEM:
Indexing rules defines which types of node and properties are indexed. An index configuration can define one or more indexingRules for different nodeTypes.
However, when I check on indexes created in We Retail project, I can see that there are nodes like this:
/oak:index/lucene/indexRules/nt:base/properties/childrenOrder

There is lucene index with many properties inside indexRules node. Every property has attribute index (Boolean) = false. Per Lucene documentation, this means that this property (in this practuculat case childrenOrder) is not indexed.
What is the reason behind this? When we don't want these properties to be indexed, why are they inside the index? If I got this right, there is no sense to put property inside indexRules (to be indexed?), and than put its index value to false (to exclude it from indexing)?