Are they? I'd be interested to hear your experience on this. So far for me they have only really been able to summarise what I could find from the top few results searching online. They do a good job of summarising that, and might be quicker, but that's been it.
However, when I encounter an actually tricky issue, like a threading bug or a null pointer exception/type error sort of generic issue that's 5 levels removed from its source, these tools never manage it. Despite prompting saying I don't need a NullPointerException explained to me, figure out how this is null, the results are poor.
This might be my biases speaking, but it really does feel like I'm speaking to something that's good at transforming words and paragraphs into different formats but which has no actual understanding of the code.