I think this child is obviously talented and as far as piano playing goes "gets it"
But it does raise and confirm 2 points.
Piano playing is not alone about finger or hand size, it's the full motion of back to shoulder right down to finger tip that's required to achieve sound. A 7 year old child can play a piece that adults that can span a 10th with no problem complain about stretches. I arguably think it's better if you cannot reach notes because you are then not tempted to stretch, but to think of other movements required to get you to be able to play a combination of notes. If anything hurts or feels unnatural, chances are you're not doing it right.
Next the bag is a stunt, that while impressive, simply confirms that the work required to play this piece is A LOT. Ultimately by the time you're playing every note 100% accurately and 100% speed, you don't really need to look at the notes.
2 reason's I think pianists (myself included) look at our hands when playing.
- We have not practiced enough to know without doubt we cannot miss.
- We don't have a natural motion with every note we play and so watch to make sure we can correctly make the unnatural motion do what you tell it - sort of like your boss coming to watch you work so you make sure you work harder, more meticulously.
I think taking on difficult pieces either too early or without correct training leaves us to "guess" the motion required to achieve the end result, and while it may still do it, doesn't mean it's correct, how many different ways can you hold a pen to right your own name... Furthermore, even when you find out how to hold a pen, how many still revert to what feels comfortable, rather than leaving their comfort zone.
There was another post about what happens to "child prodigy's" after growing up. And I think the answer is simple, there's no such thing in context of a child being "super natural" or beyond their normal ability.
A child prodigy is simply a child that "get's it" either through, luck, genetics or hard training.