"We don’t allow apps that interfere with […] or access in an unauthorized manner […] other […] servers, networks, application programming interfaces (APIs), or services, including but not limited to other apps on the device, any Google service, or an authorized carrier’s network."
"Examples of common violations: […] Apps that access or use a service or API in a manner that violates its terms of service."
I would also argue that accessing a website is not an API or an undocumented feature but a public entity. Who decides how a browser is supposed to display a website? It's up to the browser maker not some app store review process. That is why we have moz- CSS and apple meta tags.