Correct, they should remove the word "fundamentally" and then the argument probably holds. Because from what I read those training sets were quite often imbalan

Correct, they should remove the word "fundamentally" and then the argument probably holds. Because from what I read those training sets were quite often imbalanced. So I must wonder, where are the training sets coming from? Is it actually the same set, being reused? Is there somewhere a job as "training set creator"?