No, it's definitely a bug.
I've played puzzles of all sizes. Most of the puzzles I've played have been 3x5. Yet, it shows that all the puzzles I've played are 4x4. Even when I play a 4x4, though, those numbers do not go up. It's clearly showing someone else's stats.
It's a bug. Finally someone else has posted that they are having the same issue. It's over in the "Comments/Bugs/Feature Request" forum.