No, regular web search will just give you links. You have to click and go read the text. Putting together a comprehensive page of (seemingly) cogent arguments will need GenAI.
People like this will go and click those pages, and seek out communities that will agree with their preconceived notions.
ChatGPT results are just one mild manifestation of it. If and actually not if as an alternative they will find unhinged forums with echo chambers far worse than ChatGPT. At least ChatGPT isn't actively trying to rip you off to sell those supplements, and it usually adds disclaimers.
You can probably even in worse ways find likeminded communities, which are likely much more unhinged than ChatGPT and lead you down a much darker path.
There is likely enough existing information out and discussion out there. But ultimately he must have found it somewhere that this supplement could help, to go to ChatGPT with it.
I think the big difference is that with web search there will be a couple of reputable sources that will be at/near the top, like web MD and Mayo clinic. I can search and click one of those and be fairly sure it'll be accurate. There is no immediate way with chat gpt for me to know if it is reliable or crank mode.