From what you're saying, it would cause the tube to crack, not the side plate to fall off.
However, the plate is so far from the main stress point (BB shell) that its not an issue.
Another thing - why is a tube less 'dangerous' than that plate? None of the old frames failed at the ends of the seat tubes...
I'd be more worried about the head tube falling off, however, as we all know, this has not happened on any of the 'new breed' Zoo or Echo frames.