Why do web pushes look and behave differently in Firefox and Chrome under OS X?

Question

Browsers

Notification through Firefox appears in a window with rounded corners,

disappears after a few seconds and remains in the tray for notifications:

A notification through Chrome appears in some kind of custom window, with sharp corners and X to close, does not disappear by itself and does not leave traces in Notifications tray:

 
Why is that? Don't browsers use a single operating system API to display notifications?
Is it possible for Chrome to use the same "native" mechanism as Firefox (and, probably, Safari - has not connected yet).
Method in service worker to display notifications in all cases:

// ...
self.addEventListener('push', function(event) {
  console.log('Push message received', event);
  var title = 'Deserterio message';
  event.waitUntil(
    self.registration.showNotification( title, {
      body: 'event xxx',
      icon: 'i/150x150.png',
      tag: 'my-tag'
    })
  );
});

Answer 1

Yes, they use different methods for displaying notifications. In general, chrome has experimental support for native notifications, but the problem is that notifications in chrome are more advanced .
Google calls it Rich Notifications, such notifications can have several buttons, a large picture under the notification, etc. - native OSX notifications don't do that.