YouTube is a publisher because it hosts and distributes content.
There is loads of misleading crap on YouTube which I'd love to be deleted such as the dangerous climate change and new ice age conspiracy theory channels. Lots of them seem to do very well and receive lots of money in sponsorship from companies with vested interests in it. I accept there is a valid argument of leaving all of that rubbish, in the spirit of free speech, but people are often too ignorant to distinguish between real and pseudoscience.
Cryptocurrencies are frequently used by criminals and scammers because they can't be traced. I've seen videos about scammers tricking people into opening cryptocurrency accounts to pay money into. Of course this doesn't mean that all crypto currency content is a scam, but YouTube's AI can't tell the difference. The problem is AI can't explain the reasoning behind its decisions which are the result of training. People will have reported scams involving cryptocurrencies and the AI would have learned to associate cryptocurrency with scams, hence the warnings.