[paulfharrison]

Producing a diverse list of results may still help in a couple of ways here.

* If there are a lot of lexical matches, real semantic matches may still be in the list but far down the list. A diverse set of, say, 20 results may have a better chance of including a semantic match than the top 20 results by some score.

* There might be a lot of semantic matches, but a vast majority of the semantic matches follow a particular viewpoint. A diverse set of results has a better chance of including the viewpoint that solves the problem.

Yes, semantic matching is important, but this is solving an orthogonal and complementary problem. Both are important.