Apparently we don't fire scroll event on visual viewport API on macOS :(
Actually, the current behavior of WebKit matches that of Chrome so this is probably not really a bug. In fact, offsetTop/offsetLeft are always 0 on macOS when it's not zoomed. When we're zoomed, we'd fire scroll events as expected. This is somewhat counterintuitive but it's probably safe to match Chrome's behavior here.
Right, that's related to whether you fire scroll events on visual or layout viewport changes.