Summary: this looks like a web developer implementation issue Apple-side. Potentially we could reduce a jank test case but the apps are likely large and complex to reduce.

More detail:

On Android Chrome, using "Request desktop site" as described above, touch/zoom events appear to be captured and behavior overridden. There is a lot of UI jank, and the resulting user experience is notably different from what a user would be accustomed to experiencing (per bug reporter's comments). My impression is that this is an artifact of implementation decisions made by the site authors.

Potentially there is work we could do to de-jank / prioritize input events, ensure zoom out is always available, and same for double-tap text to zoom to fit. This would require more detailed reduction of test cases from (1) the main page and (2) an app with more text such as Notes or Pages. I am not sure we will end up with cases that are viable for fixing. It could be that we just find more definitively that the behavior is due to web app JS capturing certain events and not propagating. However, given app goals to ensure smooth FPS and no jank, possible we could produce a test case focused around that.

I expect this web site is designed to work best with Safari on OS X. It behaves smoothly there with both Safari and Chrome (though obviously pinch/zoom and double-tab aren't relevant there). iOS Safari produces a mobile-specific page that does not feature the app launcher or web versions of the Apple apps and I'm not sure how to request desktop site.

Notes with Chrome 55.0.2883.91 on a Nextbit Robin Android 6.0.1:

- it's not possible to pinch-zoom out beyond the 100% size view of the page
- it is possible to pinch-zoom in, and back out to 100%, though it is very janky
- multiple sub-apps (such as Pages) note that "your browser is not fully supported" in an in-page popup before allowing entry
- text such as inside iCloud Notes is not wrapped, and the viewport seems forced to a width beyond phone screen. Zooming in is again possible though janky. Double-tapping intending to zoom to fit text does not work with note text body. Often if I pinch-zoom into Notes app I get a web app implemented "modal" dialog (not true modal) popup saying "Notes has stopped responding", [error text], buttons with "Close / Send to Apple".