I don't think there is a such a thing as a mobile theme anymore, just different themes depending on the resolution of the browser window, principally the width. That looks to a quite a low resolution screen to start with, and then the browser window available is being made much smaller again. Don't have the favourites displayed and make the window use more of the screen. Anyone can see the layout switch to the different themes BTW, just resize the browser window to make it narrower and you will see that it switches to what you would see on a low resolution screen like a phone. There is of course noting wrong with using that theme on the desktop, but perhaps not what you would normal choose.