The default results set returns are ranked by relevance and will always return 250 documents or less.  If the initial results are resorted by date, the 250 most relevant documents will be resorted by date.  This sort may not retrieve all of the most recent date order documents for a topic because the initial list was already reduced to the most relevant 250 results.

This was established because the majority of queries were one or two words. Adding the hit count favors more focused articles over those recently loaded.