The problem some of us have is we get used to jumping between emacs windows/buffers using C-x o and C-x b and then without thinking about it try and use the same keys to jump between i3 windows and of course it doesn't work. Or vice versa, trying to use i3 shortcuts to switch emacs windows/buffers.
That's fine as far as it goes, but I don't think that gets you what this article is for, which is things like using the same binding context-dependently to navigate between emacs splits and regular window manager windows, context-dependently. Which is a fun bit of overengineering.
A dedicated key for all window-manager things is what people that have thought about it do (I use the "windows" key). But keyboard manufacturers haven't thought about it, so sometimes reasonable things aren't possible. I don't know.