Yes, there was one family of jailbreaks that worked like that, but you'd still need to hear about that and have some reason to want to do it to your phone, and I suspect a very small portion of iPhone owners did that. It would be a lot worse if Apple were forced to allow anyone to make what are essentially jailbreak app stores like Cydia, then one of the biggest video games ever told all their players to go install that so that the video game company can sell digital items at higher margins.

I'm glad that doesn't work any more. I don't want arbitrary web pages to be able to run code as root on my phone.

I'm glad too. But still, I don't think that has to mean "I can't run code as root on my phone".