Joe, the big brains of Medium giveth, and the big brains taketh away. Ugh. The centered logotype simply gives a more unified to the mobile app. Between you and me, I don’t mind the centered type, but it kinda leaves the header space a little unbalanced (with the Search, Bookmarks, Notifications, and avatars in the righthand corner). But hey, I can live with it. If the green monster didn’t send me running for Wordpress, neither will this design tweak.
As for the white background sans the beige border … that’s cool. That’s the way most logos live, floating on a white background. The black background is for use as a button or bug.
I think you may be right about it possibly being rushed. Maybe someone got cold feet and said “No! They like it too much! We can’t have that!”