Is he able to touch-type but simply chooses not to? Or did his obsession with keyboards never lead to him learning how? It's a mystery to me.
Technically it is possible to touch type with a single finger.
Of course, the more fingers you use, the faster you can type, probably needed to reach > 100 WPM, but I tend to spend much more time reading and thinking than typing usually, so in my case this is marginal.
I have not looked at video at all, but as a touchtypist I have a struggle not to set my index fingers on f/j.
I have seen some Internet touchtypists who claim they can use something else as keys to figuring up where their fingers are located (for example, lShift/rShift or Lenovo's clit) but in real world I have not seen any touchtypist who is not sticking his index finger on f/j constantly.
That said, what he does certainly looks like either an imitation of touch typing while pressing random buttons, or a method of touch typing that I’m not aware of. It certainly looks too fast for him to be checking every letter he types.
My error rate is pretty high due to recently switching keyboard software, but I can manage about 40-50 wpm on a phone keyboard and my main reference points are the corners.
I’d be amazed if you can do 90 wpm with just your index fingers regardless of strategy though. With two fingers and an average of 4 letters per word you need to tap 90 / 60 = 1.5 * 4 = 6 / 2 = 3 letters per second per finger (more if your words are longer).
I trust you can do it, but I can’t imagine what that looks like.