I can appreciate the motivation to fix this, but I don't see a
reliable way to do so.
EG say I sort first by Title reversed and then document size
non-reversed. In that case, should the tie-breaker (sort by docID) be
reversed or not? (Or, vice/versa).
I don't think it's well defined, because Lucene doesn't have a
toplevel (in the Sort object) reversed boolean (it's per-SortField).
That fallback ("compare by docID") is sort of an emergency
tie-breaker, to make sure you get deterministic results when your sort
One simple way to get the behavior you want is to disambiguate
your sort by adding SortField.FIELD_DOC at the end. Then you can
explicitly control whether it's reversed or not...