nummerzwei: Iīm not quite sure if this game is the best of example for your idea. It is clear there were some psychological factors supporting the weaker side in this game.
1)Padmini (born 1994) and Harika (born 1991) are both from India and the latter is rated 254 points higher. Who wouldnīt be at least a bit nervous under such circumstances?
2)Their playing styles are almost the opposite of each other, Padmini plays open positions, while Harika prefers closed ones.
Also, Harika often deviates from the main lines (at least I think so), while Padmini has quite a lot of highly theoretical openings in her repertoire, most notably the Najdorf Sicilian and the Gruenfeld-Indian as black.
This means that if one player succeeds putting her opponent into "her own" type of position, she will probably win the game.
But well, the intention to stereotypedly stick to a certain type of position often leads to unbelievable mistakes, as we see in lots of games like these.
It is quite similar to what happens when Naiditsch plays Gustafsson, for example (their score is 5-1 in favour of Gustafsson despite Naiditsch being constantly rated 50-100 Elo-points higher).
Nevertheless, I think that in principle, you are right when you say that Elo matters much less than usual in these youth tournaments.
I also donīt want to be told that I had belittled the achievment of Padminiīs, because I havenīt. I think she is extremely talented and I also enjoyed the game itself, which she played extremely well.
I would not be surprised if she was as good as Hou in only a few years.
I only wanted to show what Routs of this patricular success of hers are.