The yawing motion at the beginning of the video is because they moved the drone ship to avoid stormy seas, so the stage had to thrust sideways to retarget. In calm weather SpaceX positions the ship right along the ballistic path, so the stage only needs to pitch up and "flip."
You can also see the grid fins "pulling up" through the atmosphere to bleed off as much speed as possible. I described the optimization a while back. https://news.ycombinator.com/item?id=14288431
Fantastic job to everyone at SpaceX!
The maneuver is more noticeable with the new titanium grid fins (needed because the old aluminum ones caught fire from aerodynamic heating). Not only are they larger, but they use a "sawtooth" leading edge that increases control authority. New: https://twitter.com/elonmusk/status/879065552060260352 Old: http://www.spaceflightinsider.com/wp-content/uploads/2015/12...
They also happen to be the largest titanium forgings in the world. https://forum.nasaspaceflight.com/index.php?topic=42544.340#...
In this case, it's "given enough initial velocity and control authority, even a brick will glide", but the spirit is the same.
A few years back a group of engineers decided to prove this by attaching a number of solid fuel rocket engines to a port-a-potty and launched it to great applause.
The goal of this maneuver to lengthen the descent path, which in the absence of an atmosphere would be a pure parabola (or more accurately, a suborbital ellipse). Passing through more air means shedding more velocity due to drag, and therefore less fuel is needed to land. Geometrically the best way to do that is to pitch "nose up."
No drawing skills except shitty MSPaint, but that's never stopped me before. https://i.imgur.com/VLYXDOf.jpg