Yes, treating AI answers with the same skepticism as web search results is a decent way to make it useful. Unfortunately the popular AI systems seem to be using multiple times as much energy to give answers that aren’t even as reliable as google used to be.
Back in the day google was using the same ‘was this information useful’ to return results before the SEO craze took off.
And yes, if the stains look like rust and there is a gap then there was a ferrous rock in the mix that rusted away. I have a spot on my sidewalk and a stone slab thing, and found out what caused it from someone who works with those materials!