It's not the browser ... the iOS app doesn't yet have the capability to scan the QR code to link your account to the website

> They have been much slower adopting features than the competition.

It's not a matter of speed. This seems to be using WebRTC for handling communications between the phone app and the browser. Safari has chosen not to implement WebRTC and so far it is still not a proper standard so I can see why. Google, as the developer of WebRTC, will obviously support it right away. Note that no browser other than Chrome can be used as well.

Wait, you know that WebKit is spearheaded by Apple? And that there's two completely unrelated problems here:

1. The frontend only works on Chrome for desktop (it appears only because it uses the non-standards track filesystem API)

2. The backend service and mobile app does not work with iOS (it appears because it uses background networking)

They may seem related, but they aren't.

That doesn't seem likely to me: what features does iOS not have right now, that this is likely to use? It seems more likely if they are targeting chrome only they did it to avoid the support overhead of making it work in multiple browsers.