Retrieval, not generation
A chatbot given your document will answer in fluent prose that may or may not reflect what the document says. When the question is 'what is my notice period', a confident wrong answer is worse than no answer.
This retrieves. It finds the sentences most relevant to your question and shows them as they appear, so the answer and its evidence are the same thing.
The trade is real: you get passages rather than a tidy sentence, and you have to read them. For anything consequential, that is the better deal.