kinematics - When this CD is spun so fast that it shatters, why does the warped shape move slower than the surface?

In this video where a CD is spun abnormally fast to the point of shattering, one notices from the writing on the CD that the surface is spinning faster than the warp "shape" is. In other words, the shape the CD has warp into is moving in a circle, but not quite as fast as the surface of the CD. What's the explanation behind this de-synchronization?

I would expect the warp shape to either not spin much at all, or spin at the same speed as the surface of the CD.