I'd never use a password manager built by Apple for the same reason I don't use Chrome's password manager or Firefox's password manager. All these passwords managers have strong incentives for "working best on ™". I want a password manager independent from any platform like Bitwarden or 1Password, because it's actually valuable for THEM to target all the platforms they can.
Apple is the only one of those three that restricts their software to hardware that only they sell. So in that case I do understand your position.