This particular move takes something that is possible in web applications today and makes it not possible in the future (offline capable frontend-only applications), making the gap between native applications and browser applications further, so developers who need to build apps that works offline on iPhone, will only be able to use Apples own technologies for doing so, in a non-cross-platform way. Which in general, is what Apple always been favoring.
Google Docs doesn't really work offline, so it's not impacted by this change. Could also be a change of heart from Apple, since their stance on web applications have changed before.
People who want to track users will always find a way to do so, it's a endless cat-and-mouse game. Now they will just use cookies instead... The only way to win this is to legislate away the freedom to track users by using privacy-invasive methods. That's the only way that will work long-term. But that'll make half of the internet industry disappear, along with it's shareholders, so it's unlikely to happen.
Now I'm not a native English speaker, but seems "arbitrary" means "determined by chance, whim, or impulse, and not by necessity, reason, or principle". Introducing a law to protect peoples privacy would not be arbitrary, especially since most countries have a due process for introducing laws.
They could restrict these APIs to "installed" web apps via the web app manifest file, if they were to adopt that. Maybe they will in the future, but for now they've just made web apps far less powerful.
Google Docs doesn't really work offline, so it's not impacted by this change. Could also be a change of heart from Apple, since their stance on web applications have changed before.