Configuring the new display modes in Drupal 8
As you've found out through comments, the title is currently hardcoded.

The reason for that is that the title isn't controlled by the view mode in the default behavior. It's whether the node thinks he's on his own page vs. not. A behavior that's not easily configurable.

Would have been nice to fix that but like many other things, we didn't enough time.

Apart from using templates to do, you could also consider to use Display Suite, just like in 7.x, it allows you to control the title, pick from different layouts and so on.