Pseudo labeling is an interesting technique and the code you provided is interesting too.
However i strongly disagree with your conclusion. The competitions had a huge leader board shake-up. So saying you had a gain on the leaderboard is simply false. You finished 2551/3835 and lost 759 places on the private leader board. Therefore saying that pseudo labeling improved your score is in my opinion not right.
Moreover i haven't seen yet any Kaggle master use this technique in order to improve their model.
