Oh and I should clarify the results as shown in calibre are already ranked by the bm25 algorithm so when you get multiple results for a query you should start with the topmost one. Generally it will be more relevant than subsequent ones. What you are asking for is basically using a simpler relevance ranking by number of matches only rather than bm25. I looked into this and I dont really see how that would be helpful. That said, its not out of the question to provide such an alternate ranking, but its not worth the effort to me, patches welcome.
Here is a technical writeup on how bm25 works:
https://www.elastic.co/blog/practica...-its-variables