Despite the cross-contamination spin in your analogy, it's just that. In actuality, the subset of users who are die-hard Safari fans can just keep using Safari if they so please without third-party web engines affecting them in the slightest (they don't even have to download other browsers).
“We’re banning vegetarian restaurants. Too bad if some consumers want to eat in a place with no meat: if you don’t want meat, don’t order it. Restaurants have to serve it because the government says so.”
Once the regulation forces the kitchen to serve meat, the “vegetarian kitchen” doesn't stay the same while meat-eaters use a separate space. The whole kitchen must be redesigned, staff retrained, and safety protocols rewritten. It changes the risk profile for every customer, even if they never intentionally order meat. Mistakes happen.
Same deal here. Contrary to your claim, every iOS user is impacted whether they download a third-party browser or not. Allowing alternate engines isn’t just adding an app to the App Store. It changes OS-level APIs, the security model, and update cadence. The platform Apple ships to all iOS users is now different, with a larger attack surface.
Part of Apple’s brand promise is controlling key system components so they can maintain a consistent, high baseline of security and performance for
every user. The browser engine mandate removes that control meaning updates, security patches, and optimizations now depend on third parties and their timelines, not Apple’s.
Some users downloaded an alternate browser years ago, have forgotten it's still installed, and will get an update that suddenly exposes them to new risks. Others will install Chrome simply because they recognize the name, unaware they’ve traded away battery life, performance, and certain security protections. When their device’s battery life tanks or they get malware, they’ll blame Apple, not Google, and certainly not the regulator that forced the change. Part of Apple’s value proposition is “we help keep you safe.” This mandate strips that away because regulators think they know better. They don't.
In fact, Apple knows its customers and its OS better than Japan or the EU does. There are legitimate security, privacy, and UX reasons for limiting browser engines. Just because you don't agree with those reasons doesn't mean they aren't valid. The more popular completion allows what regulators want. If anyone is that upset about it, they are free to choose the competition. That's how the free market works!
This is textbook over-regulation.