The reason they have these requirements is because they want someone who A) has gotten some sort of commendations, yes you can get them sometimes for nothing but people get a lot more by being helpful and a good player. B) they want someone who has experience in all roles explaining this is why, as say a tank, you want to do this; because it helps healers since you do that, it helps dps because you position like this: basically, you have the knowledge from all 3 classes to help explain things to any three types your mentoring. C) they want you to have ran over 1000 things so you are very familiar with mechanics and can easily explain how or why to do something in every instance. Sure you may start late and still understand things. But wouldn't someone want a mentor with a LOT more time spent learning and playing content?

Anyways, point is they want people who have went the extra mile to explore everything the game has to offer. Its pretty easy in my opinion to see they want people who really want to learn everything teaching others. And that's good.