Here is a video showing Raonic's wrist before and after impact. I would not call that a 'snap' or much wrist motion/bending at all. Serve type & whether a fault are unknown.
The best stop action single frame on Vimeo can be done by pressing the play-pause button as fast as possible. The arm passes by around second 7. (It took me 10+ tries to catch impact.)
From behind, high speed videos show that the angle between the forearm and racket (β=20-30° at impact) changes extremely rapidly as the arm rotates so that the forearm and racket become much more in a straight line (β~0°) roughly a hundredth(?) of a second after impact. See other serve videos taken from behind.