Absolutely, he can't (and that can be a good thing). How do you know how a staccato in a Beethoven piano sonata really sounds?
Do you mean "how a staccato in a Beethoven sonata sounded to an audience member listening to the composer himself play it"? Because I don't at all understand what it means to say what a notated piece of music "really" sounds like.
the original question had to do with how a composer expresses his wishes
as well as possible so other performers interpret it correctly. What a
pieces "really" sounds like is another question, most likely much more
complicated, I guess.