You check the information you decide should be verified.
An LLM response without explicit mention of its provenance... There's no way to even guess whether it is authoritative.
Actually, it might be fully unbounded even for an n of 1.
What do you even use for double-check? Some random low-quality content farm? A glitchy LLM? An dodgy mirror of official docs full of ads? Or do you actually dig the source code for this?
And do you keep double-checking with all other information on the page... "A TOMLDecodeError will be raised on an invalid TOML document." - are you going to start an interactive session and check which error will be raised?
Just because you can find multiple independent sources saying the same thing doesn't mean it's correct.
In all honesty doing this for news and such brings me comfort. Because the truth is usually pretty vanilla.
"What I tell you three times is true"
Part of why I prefer to use a search engine is that I can see who is saying it, in what context. It might be Wikipedia, but also CIA world fact book. Or some blog but also python.org.
Or (lately) it might be AI SEO slop, reworded across 10 sites but nothing definitive. Which means I need to change my search strategy.
I find it easier (and quicker) to get to a believable result via a search engine than going via ChatGPT and then having to check what it claims.