Well I had a listen and it is phenomenal and a bit mechanistic BUT as already stated, get the technique learned early and the rest will follow; and as she now plays Jazz, she has clearly picked-up something along the way.
But music is also an interpretative art where you can either play exactly as it's written-down (which is one school of thought I'm sure) or you can build extra feeling or mood. Only the original composer can play or say how it should be.
My Saxophone teacher had to rein-in the feeling and hammer-home the technique!
Not sure what to make of the guitar playing kids though. Amazing, but whether it's healthy is another matter....
Oh, I don't think there's any question that the guitar playing munchkins are unhealthy...I think my friend's contention would be that Mayuki Miyashita's piece, like theirs, is fundamentally unmusical - that, to quote your eloquent expression upthread, it comes across as 'like one machine playing another'. Arguably interestingly, in light of your comment that she now plays jazz, she's first & foremost a classical pianist - and a highly rated one. I say arguably interestingly because this whole thing started when I googled out of idle interest wondering what classical pianists think of, say, Oscar Peterson or Art Tatum, and stumbled across
this thread. Where, among other things, it was suggested that while most jazz pianists, having started out learning classical, like everyone else, can turn their hands to a bit of Mozart if called on to do so, most classical musicians regard jazz with a degree of fascination, but are quite unable to play it. So as a genre-straddler, Mayuki is a pretty rare beast by any standards - let alone those that apply to pre-teens.