1. Electronic flash normally only works UP TO the max X-synch speed of your camera...typically only 1/200 sec for Canon FF cameras (or 1/250 for Canon APS-C cameras)
2. Electronic flash normally falls off in intensity according to the Inverse Square law. For example, with a Canon 580EXII set for max telephoto (105mm on FF), its Guide Number is 190, which means it will be usable only to about 67' when shoothing with f/2.8 on your lens and the camera set to ISO 100 -- even though it allows f/22 to be used when you are only 9' away from the subject!
3. When using flash outdoors, you also have to consider the fact that the ambient light may itself overexpose a photo when set to the shutter speed and aperture; for example f/2.8 1/200 would be overexposing by 4EV if your subject were in bright sun (even without the flash)!
4. HSS allows a flash unit like the 580EXII to be used with a faster shutter speed than 1/200, but when you do so, its effective power is diminished a lot! For example, shooting at 1/800 would cause the effective Guide Number to be reduced so much that its max distance it could reach with f/2.8 shrinks from 67' to only about 16' (or less)
5. The lights which are shown in the linked video are NOT speedlights like the 580EX, but are much more powerful studio lights, and they do NOT support HSS and therefore are limited to the 1/200 shutter speed.