High school is relevant for people don't do much after high school. It shows the level of expectation they have for their candidates.
How do you deal with adversity? How do you deal with peer pressure? How do you motivate yourself to work on things that feel irrelevant? How do you choose your hobbies and the people you associate with? Those are important things to assess in a potential colleague. And this is just one potential angle on how one might assess them.
As for "making stuff up that sounds good", you are correct, some people are better at that than others. Fortunately we have clear and objective measures of that to work with so forewarned is forearmed.
Odd that Canonical would want such people.