It sounds increasingly like your definition of exposition is "stuff that bores me."
One could also say that it sounds from your arguments like your defintion of exposition is "stuff that isn't plot."
My definiton expostions hews very close to Merriam-Webster's, actually. They say it's "a setting forth of the meaning or purpose," which strikes me as fairly dead on. Exposition is the author puting aside the story for a moment to explain something. If your foreshadowing is done in a plainly ovbious way, than it's exposition. If you subltly work it into the narrative in such away that the reader exclaims some form of "Why didn't I see that coming! All the clues where there!" then it's not.
Is it boring when authors stop the story to explain where we are, who we're talking to or why we're talking to them? Sometimes. Depends on how good the author is.