Ali I think you may have actually identified an issue. What leads to me think that is the fact that tablets can’t make use of hover effects, so it doesn’t make any sense to use the desktop menu design at the tablet screen size.
This functionality was correct up until the 2.1.3 update so I’m thinking it may have been removed for testing purposes and just never added back in for some reason. I went ahead and created a feature request for this to be updated in a future patch release. You can track it here.
While it is possible to change the functionality using media queries and other custom CSS this approach seems to cause other issues. Another possible solution for the meantime is searching for a plugin that adds the hamburger menu functionality in the WordPress repository.
I wish I could have been of more assistance to you. Please reach back out to us if you have any other questions.