But you never mentioned that you need changes in Mobile view , you only asked "How do I Change My Article To Full Layout? " , am I right. And besides it doesn't must be a BUG as you may think, but designer concept (evidence below with template.css styles), the same example as you have with your Phone Applications. However, unlike the look of the app on your phone, on the Joomla website you can change almost everything, adjusting it to your vision. It's a bit like building with Lego bricks, if you know what I mean.

Spaces and font-size can be changed in just 4 lines of Custom CSS, if you think they are too big. Just use Code Inspector from your browser , check class name what you want to change and override that using your own @media style.