TDD is a development methodology, not a testing methodology. The main thing it does is check whether the developer implemented what they thought they should be implementing, which is not necessarily what the spec actually says to implement or what the end user expects.

It's still a useful technique and way to apply testing to development. But yes, it's not the best resource in telling you what tests to write, more about how they can be applied effectively. Which is a skill that seems absent in many professionals.