Fixed size chunks is holding back a bunch of RAG projects on my backlog. Will be extremely pleased if this semantic chunking solves the issue. Currently we're getting around an 78-82% success on fixed size chunked RAG which is far too low. Users assume zero results on a RAG search equates to zero results in the source data.
Agree, BM25 honestly does an amazing job on its own sometimes, especially if content is technical.
We use it in combination with semantic but sometimes turn off the semantic part to see what happens and are surprised with the robustness of the results.
This would work less well for cross-language or less technical content, however. It's great for acronyms, company or industry specific terms, project names, people, technical phrases, and so on.