the girl in the video is a model... im sure she knows (at least to a certain extent) to apply mascara, lipliner and eye liner. When it comes to teaching a costumer yes, but for a video that promotes MAC products that mostly relies on the fact that people think its the best because "the PROs use it" people want to see PRO performance.
We learn more from watching a professor solve an equation explaining the steps, than watching a classmate doing the same thing. It's all about image. I went to make up school in Madrid, Spain, and I had many people coming to "learn" how to do their make up, but in the end to be convincing and trusted as a make up artist you rely on the precise and more authoritative application of the make up.
If I see this MUA teaching a customer i'd be like, cool so she is teaching, but if I want to see a promotion of a product I want to see the PRO, especially is they are senior artists. I didn't have clients do their liner, because then I wouldn't have gotten my certificate. she can teach her later, not in the video. thats my honest opinion.