Interesting. Are there any necessary abstractions?
It's a matter of degrees, but eventually you need to abstract something in order to keep the game playable. For example, even if you know that you swung your sword twice and that one of the swings caused meaningful injury, that doesn't tell us
anything about the location of the wound, and very
little about the severity of the wound. Hit Points are still
somewhat abstract if we say that all damage has a physical component - the proportional HP method - even if it's
less abstract than saying that they are some unknown/unobservable combination of physical and non-physical components. If we tried to add a hit-location system, to make it
less abstract, then that adds complexity and bookkeeping and it would still be somewhat abstract.
Since the point of a role-playing game is to play a role, we need enough detail that we can make the same decisions our character would, and for the same reasons; if the player and the character are operating on different information, then that can cause dissociation as the player tries to figure out what the character actually knows, so they can try to make decisions from that perspective. If characters don't know that there's an easily achievable plateau of fighting skill, which is the in-game reality reflected by five levels in a fighting class, then we're left questioning what the characters
do know. Are they capable of observing that the efficacy of a fighter doubles at a certain point of skill? And if not, then
why not?
