most of the magic of the hand interactions comes from a seemingly endless amount of animation and bone rigging done. The hands animate against basically everything, which goes a long way towards making your brain fill in gaps. My buddy across the state is playing with a windows VR headset, he was asking me earlier how the game could "figure out what his fingers were doing" when he'd do things. The game isn't actually tracking his fingers, it's just that it's really, really good at predicting what you want to do and having the fingers match even if the controller has no tracking ability for that.
I'll give an example with the index controllers from the very beginning of the game. You start in front of a radio, and when you move your hand towards the dial, even on the index controllers which do full finger tracking, even if you don't move your fingers, as you get closer to the dial, your hand's index and thumb start to move like they're anticipating grabbing the dial. It works because, IRL, most people who are going to grab that dial will position their fingers like that naturally. The animation happens with the index controller even if you don't move your fingers that way. Those kinds of animations fool you into thinking there is an insane level of finger tracking going on.