RAG is a technique, so instead of string matching (like grep), it uses embeddings + vector search to retrieve semantically similar text (car ≈ automobile), then feeds that into the LLM. Tool use is broader, RAG is one pattern within that, but not the same as grep.

Yes, you are right. The OP has a weirdly narrow definition of what RAG is.

Only the most basic "hello world" type RAG systems rely exclusively on vector search. Everybody has been doing hybrid search or multiple simultaneous searches exposed through tools for quite some time now.