Since the scale is only 1-5, saying that only a few people in the world qualify as a 5 or even 4 wastes 20% or even 40% of the expressiveness of the scale, which makes it pretty useless. It's better to round in the other direction, and think of the scale as logarithmic. If most people in the world won't have any ratings in the 4-5 range, that makes it pretty useless for comparing your own proficiency in the languages you do know, which is the entire point of the exercise, not comparing yourself to the people who designed the language. The interesting thing she's trying to express is how much better she knows JavaScript than Ruby, not how good she is compared to Brendan Eich or Matz.