Just to clarify, there is no way the system, as it is, says “A beginner is 13k”
What it says is that every new player is very uncertain rank, somewhere between 7k and 19k. IE 13k +/- 6k.
There are two problems with this:
The rest of the system (especially player-matching) doesn’t take the uncertainty into account.
The range isn’t broad enough, and is biased in the wrong direction. New players are more likely to be TPKs.
This doesn’t change the conclusion, just clarifies, in case there was the idea that the system says beginners are 13k.