While that is true, offering the option to change the default might still be enough to avoid any anticompetitive claims (which I think was the point the GP was

While that is true, offering the option to change the default might still be enough to avoid any anticompetitive claims (which I think was the point the GP was making). That said, Microsoft were still forced to present a randomized list of browser options to the user upon first install so there is also precedence of changeable defaults not being enough to satisfy complaints of anticompetitive business. This is all hypothetical though because it's still far from clear that Apple have ever wanted to enter the search market, let alone got paid not to, let alone what might happen to the iPhone if they did.