This program is definitely not anywhere near 1500-1600, or even 1800-1900.
It's so difficult to draw it already!
Here's my most recent effort, after some 6-7 very humiliating losses (including the one above)
Of course I play fast and stuff, but still - no 1900 would deal me a 7.5 - 0.5 score, no matter how fast I would play.
That play.lczero.org doent learn from human games. It is impossible to learn from random opponents. Leela already had 1.5 million self-play trained games. She can learn by playing against herself(exactly similar opponent). How she learn. In first game 1000 games, she will play f4, and another 1000 games she will try e4. And compare the winning percentage. If e4 gets more winning scores, she will prefer e4 than f4. In random opponents, let us say she play against 3500 stockfish, whatever move she make, she lose. She dont know which one is stick vs carrot. And the same, if she play against 500 rated opponent. whatever move she make, she win. She may not know which move made a difference(win or lose). She cant learn stick vs carrot again.