Someone in my company spent the past month setting up ChatGPT to work with our company's knowledge base. Not by a plugin or anything, just by telling ChatGPT where to find it. They didn't believe that ChatGPT was making any of it up, just that sometimes it got it wrong. I stopped arguing after a while.
Sounds like there are two misconceptions there: the idea that ChatGPT can read URLs (it can't - https://simonwillison.net/2023/Mar/10/chatgpt-internet-acces... ) and the idea that ChatGPT can remember details of conversations past the boundaries of the current chat.
This is something I've noticed too: occasionally I'll find someone who is INCREDIBLY resistant to learning that ChatGPT can't read URLs. It seems to happen mostly with people who have been pasting URLs into it for weeks and trusting what came back - they'd rather continue to believe in a provably false capability than admit that they've wasted a huge amount of time believing made-up bullshit.