From the article:
Your eyes are your mouse when using the Vision Pro. When typing, you look at a virtual keyboard that hovers around, and can be moved and resized. When you’re looking at the right letter, tapping two fingers together works as a click.
So they were working backwards to determine the inputs based off of the observed eye motion.
I have a much less modern VR headset and you can definitely still type on a regular keyboard while you’re wearing it. You can’t see the keyboard though, so you need to be skilled enough to touch type. I can’t find any reliable-looking statistics on it with a quick search, but it seems like that is not a very common skill
Touch typing. Like I said I cannot find any reputable statistics. touchtypeit.co.uk claims “according to research” it’s less than 20%, but does not actually link any specific research. There are some other sites like it that are trying to sell you a product and list a low percentage, but I can’t find any actual studies or statistics