I think in many cases there are other factors involved too. The majority of shaving vids that I've seen feature men with light, sparse beards. As well, they usually seem to have very minimal growth to begin with, to the point where you have to wonder why they are bothering to shave in the first place; this offers very little resistance for the blade, so they get this long sweeping strokes for the camera. And to be fair, we can't tell how close the resulting shave is
Remember, very few shaving vids are done for educational purposes. Most are for fun or simply to show off to friends and strangers. I'm sure some have even taken some, oh, "dramatic/creative license" for that very purpose.