> World class hacker that literally types one finger at a time, like she had never used a keyboard before.

Vladimir Horowitz very famously played a televised concert back in the 80s where, for the first time, a few cameras stayed focused closely on his hands. He had horrible technique. It was horrible by his own professed standard: for most of the fundamental things he himself taught to his students, he was doing the opposite! This was broadcast to millions of people. Piano teachers everywhere were pissed.

While that bad technique isn't particularly noticeable in the resulting sound for that concert, there's an analysis somewhere that shows the damage it did as he aged. You can hear certain problems he was having in his later recordings, and video from the same period confirms that the bad technique (like straining the wrist on octaves) was the culprit[1].

In any case, all kinds of world class people do all kinds of fucked up shit.

Edit:

1: In other words, when he was middle-aged he could play octaves accurately with a strained wrist, but he couldn't do that in old age. However, if he had been leveraging the weight/power of his entire arm for the octaves, he would have gotten accuracy in both cases.

2: IIRC, he didn't realize what his technique looked like until someone showed him the video. :)