But that means that the error is independent of the search term. That's not my experience. Of course you can't trust it 100% but I think it's pretty good for easy searches to a degree that I would trust it to be correct. You have to get used to the tool. If the accuracy is good enough for easy search terms for people to get some use out of it, then we have a product I think. Of course it's probabilistic but even wikipedia is wrong sometimes. These things won't be correct, it's always an approximation, but that's also a reality of live. Information is inherently unreliable and so are our tools.
Just view those tools as you would view humans. They help, they can be wrong, and if you need confidence you have to get some sources. At least that's how I would view them.
Wether this all works out is another question. But it's an approach different to search as it exists and may complement it. People thought Siri would revolutionise everything and then it didn't.