The exercise you are looking at is based on the chromatic scale. This is a very good yet extremely simple exercise to do. Why is it used so often is that you'll se a lot of gutiar players use the 3 notes per string scale pattern. That will sometimes leads to a loss of dexterity in one of your finger.
I'll take myself as an exemple. For years I've practiced 3 notes per string scale exercises and I found myself using my middle finger most of the time.Because of that I ended up with an underdeveloped ring finger. With this chromatic exercise you are training both fingers the same way.
It's true that it might not be the coolest exercise but it's a very important one. My suggestion would be to use both 3 notes per and chromatic. That way, you'll have the best of both world.
As far as the video goes, the only way I can see that someone would not bend his wrist is to bring your elbow closer to the guitar. That would mean that all your body would be closer to the guitar and that you hold you guitar very high.
Also, why most teacher ask to have your finger has perpendicular is that the more straight angle you have, the less chances you are to hit the adjacent strings.
Hope that helps you out.