Do you really think that this is a serious obstacle to phishers? They're not going to just throw up their hands and say "Welp, passkeys...I guess we're done making billions of dollars a year,."
I don't think so. I think they'll just engineer (socially and technically) their way around it, e.g., "we have a new domain, please set up a new passkey to keep your account secure" will likely work just fine.