Incorrect! On macOS any browser is acceptable and they’re all running their own HTML, JavaScript, and CSS engines. So long as you leave the (these days read only and cryptographically signed) OS portion of the drive alone you can install or run whatever you want on a Mac.
But on iOS, you have to use WKWebView to render any HTML. No 3rd party engines allowed. They keep iDevices pretty locked down to minimize attack surface and preserve RAM usage.
Apple’s App Store policies state: “Apps that browse the web must use the iOS WebKit framework and WebKit Javascript.”
This means that web browsers can’t implement their own rendering engines; they must embed a version of Safari’s rendering engine. They can’t offer a faster rendering engine or new web features. In effect, each third-party browser on iOS is a different interface around Safari.
I’m not sure if you are agreeing or disagreeing with your reply. It backs up what I said, so maybe agree? But you felt the need to reply so maybe disagree?
Apple laptops run macOS, so FREEEEDOM. But Apple tablets run iPadOS (iOS variant), so lockdown.