Personally no, I don't think so. A similar discussion came up years ago by a bunch of chess players with similar arguments (stamina, focus, etc.). Clearly different sports have different levels of physical fitness requirements. But, in my mind, the key component to a sport is the physical exertion. Not that there's zero in pinball, but just so little I wouldn't think it qualifies.
Doesn't mean it still can't be great competition, though.