As an aside, there's now Lance data format support in DuckDB through their extension. It has Lance's vector search support available among other things:

https://github.com/lance-format/lance-duckdb/tree/main?tab=r...

I just noticed this, and your post, and haven't yet checked neither (sorry). I'm however doing some vector search benchmarking soon, with DuckDB's options alongside others. So your work caught my attention here.