Earlier quoted context omitted.
And rotating a tangram on the iPad takes two touchpoints, where the physical one can be rotated with a single finger.
Auto-snap, and most importantly inability to rotate, allowed my 1.5yo kid to solve puzzles when he wasn't yet able to solve wooden puzzles well. After an intense period of solving those non-stop (I believe it's first time he strongly experienced the positive reinforcement of winning a game), he also easily does the wooden puzzles. I don't have any data on whether that's indeed a win developement-wise, but I'm excited…
That said, I do see what they mean about rotation. My son took some time to learn to play Amazing Alex (Rovio's Incredible Machine remake) because of the clumsy rotation UI in that one.