Fair question. When we built our first vector extension, pgvectorscale, we actually reached out to pgvector's author to see if they'd be interested in supporting additional index types (at the time, DiskANN-based), so we could contribute our work directly to pgvector. At the time, their preference seemed to be to focus on the existing index types rather than expand the project in that direction. We respected that decision and went ahead with a separate extension.

But one of the great things about open source and PostgreSQL's extension architecture is that these projects can coexist! pg_vectorsearch can work directly with pgvector's existing data types, so developers can use either index.