Grounding is the right idea, aimed elsewhere
NotebookLM's core discipline — answer only from the sources provided, cite them, refuse to invent — is exactly right for studying, and it is the reason students reached for it before anyone marketed it to them. NoteLinkAI's Study Buddy works on the same principle for the same reason. The divergence is not about answer quality; it is that NotebookLM is a research notebook that students are using as a study tool, and it was designed for a researcher with a pile of PDFs and a question, not for a student with five courses and a date in December.