Very poor ergonomics as evidenced by the player's difficulties.
Not really, that's his choice to use the keyboard that way. In the demo he's using NI B3 and Linux Sampler in COMBI mode by the sound of things. Neither of which require you to touch the screen at all as the control panel is mapped to the software.
For example, he's using the sliders to turn on and off sounds by adjusting the volume, rather than just pressing the dedicated mute buttons for each track. He could also have used the program up and down buttons too if he wanted to.
I don't quite get why he's using the keyboard this way, but if it works for him well that's then that's all that matters. Me personally, I would do it differently but either way, there is nothing wrong with the ergonomics.
It's his choice to use the keyboard the way he is using it and that's all there really is to this.
Regards
James