I think the difference is really that the mechanics are more abstract than the character's experience.
For example, if the mechanics dictate a hit (and further provide damage and hit poit values), there are many different ways that could be narrated. The character experienced only one of those however. It's common enough that we who are playing the game call it a hit and move on, while the character is keenly aware of how many thrusts he made with his weapon, how many made contact, and a variety of other contextual details.
However, hitting and missing are mutually exclusive states in the mechanical realm, and I think that follows in the world as well. If you hit, you did something that caused harm (whatever that may be), and if you missed, you unambiguously failed to do so.