Never said they could fall out (by themselves, that is), but I'm glad you asked in a civil manner (this is a big compliment to you, mj...too many people nowadays just give other posters the third degree...happens too much on forums these days).
If they were all hand-threaded (installer forgot to torque them), they'd all eventually back out a couple millimeters. Then the plate would move in that direction. They back out another couple millimeters, followed by the plate once again. Because of the limited clearance, once this starts, the plate can never again "flush up" with the face of the crank axis, and the problem quickly gets worse until either it falls off, or in this case reaches the limits of how far the TC can lateraly move (it'd stop moving towards the direction of the A/T case for the Honda, as far as I can tell).
While I was looking through the diagrams, I noticed that this thing is nothing more than an "upsized" HondaMatic tranny. These things were uber reliable on older Accords and Gen 1 Odys. I guess there is a lot to the assertions by many OdyClub members that all the extra weight of the Gen 2 van, and in turn generated heat, is tough on these things.
OF