Hmmm, that's a curious statement for someone who's claiming to be new around here. Been around before? ;-)
Ever heard someone say "That's the dumbest joke ever," or "that's the lamest excuse ever"?
They're not literally claiming to have heard every joke or excuse of all time! It only means to convey their take on what they've just heard.
That's what I just did. Sorry if I'm confusing the hell out of you.