Are you referring to the approach of creating hypothetical questions for embedding along with the document. Or more along the lines of creating summaries of the documents during indexing and embedding those as well?

Either case, the reason we don't do LLM based transformations during indexing time is that we hope our tool can be used by teams with a lot of documents. It becomes prohibitively expensive to run these transformations at indexing time when the scale can be multiple millions of documents.