Yes, happening to me too. Sebi has been making a lot of changes to the layout of the site, in an attempt to make the desktop layout work better on smaller screens. The following is pure conjecture, but it's possible he's working toward a unified layout, instead of maintaining a separate desktop and mobile experience. I for one would +1 that goal. And that would explain why he's made the mobile layout the non-default option.
In any case, you can still open to the mobile layout by default if you have ?mobile=1 appended to the URL. My browser (Chrome on Android 7) starts learning that version of the URL once I've typed it enough times, so as soon as I start typing "Deckbox", it already has that appended. You obviously could also use things like bookmarks on your home screen.