He’s not complaining about slowness, otherwise he’d say something like ‘we tried FAISS and it was still too many milliseconds per lookup’. If his embeddings are bad, then even an exact nearest-neighbors lookup by brute-forcing every possible match (which, as you say, is more feasible than people usually think) won’t help. You’ll get the same bad answer.
That won’t help if his embeddings are bad:
He’s not complaining about slowness, otherwise he’d say something like ‘we tried FAISS and it was still too many milliseconds per lookup’. If his embeddings are bad, then even an exact nearest-neighbors lookup by brute-forcing every possible match (which, as you say, is more feasible than people usually think) won’t help. You’ll get the same bad answer.