you can see all variants but no puzzles, why?
I think because it is so easy to cheat on the puzzles.
It is allowed to use engine for puzzles, it isn't a cheat, so everyone could be at the top super-easily.
it cannot be the reason.
cheating? who cares about cheaters and they training elo?
would a graph make higher number of cheaters?
i doubt it much. you can see the training rating of any player now so if they want to cheat they would do it even right now.
I agree with showing the training rating in the graph, even if just a gray line. Can't see the harm on it.
Having a difficulty option in the opening trainer would be good too.