Nothing much different than e.g. Chrome suggesting a password and saving it?

This is not that. This is an agent autonomously navigating through the website to change your password. You don’t even need to be navigated to the site. The app gives you a list of sites with insecure passwords and you just hit a button labeled “Change” or something like that and it kicks off a process to change it. If there’s was a standard API for changing passwords, then sure. But this is far beyond just suggesting a strong password and offering to store it for you when you are navigating the site yourself. And given how often THAT simple functionality goes wrong, in my experience, I don’t have a lot of hope that this will work out well. To be clear, that’s not Apple’s fault. Some sites have garbage authentication and password change workflows.