And where exactly does it show your hostname there? And are you sure you never used it as an account name or something like that? I can’t imagine they can access the hostname from JS.
One of these days I'm gonna log in with the debugger active.
I'm not sure why they would go to the trouble of getting the web app to talk to the phone app directly, but it is possible.
I don't have any banking app installed on either device.
It's confounding.