[hulke]

The "four to five" hours they mention is probably the time required to setup the grinding center, maybe dress the wheels, do some fine adjustments on the grinding process. Once the machine is setup, grinding each drill is just a few minutes.

The grinding machines they are using seems to require quite a bit of manual handling, but cnc grinding center where everything is automated also exists.

Actually, the grinding of the flutes is shown very briefly around 3:35. Filming this operation on such a small scale is difficult because of the geometry of the system and the grinding process: the drill blank is supported from below to prevent the carbide from snapping under the load, and the wheel grinds from above. The grinding wheel is order of magnitudes larger in diameter than the diameter of the drill it is grinding. Also, everything is flooded with cutting fluid.

There are hundred of videos showing the process on youtube if you look for "cnc grinding drill".