A browser is more than just an app, it’s an application runtime that executes arbitrary code downloaded from the internet. It’s the closest thing iOS has to an unregulated open App Store, that happens to only run apps written in JavaScript. With native apps Apple has the opportunity to inspect and profile them before they hit the phone, and pull them if necessary, but not with web apps.

As such the only way Apple has to manage the power and compute consumption of such apps is through control of their runtime environment - the browser.

I’m not saying their policy is right or wrong, but that’s the argument.