I dont get why you dont understand. I am not saying to charge every corner cause then you will be like the guy from your vid going fast in slow out. Maybe
@VFOURMAX1 is right and were both interpreting things different.
The fastest way around track is to be as fast as possible trough all fases of a corner. The slow in fast out technique focuses on being as fast as possible on exit, its a great technique for beginners but advanced drivers should focus on entry and apex as well wich are harder to master. Of course there are many corners where exit speed is most important but that doesnt mean you need to go slower then possible just to be sure you will get that good exit. It just means you need to take a different line and aproach for these corners while still carrying max speed trough all phases of the corner.
You go in as fast as possible and get out as fast as possible. If the corner leads up to a straight you go in as fast as possible to still get out as fast possible. But you dont go slower in just to get out fast.
Whenever you go slow in fast out or like the guy from you vid fast in slow out you are loosing time.