I don't think it's the fall that matters. The problem would come when the airplane begins to tumble. Rip the tail off a B-52, and I would expect it to rapidly tumble and subsequently disintegrate with unpleasant consequences for those inside. Furthermore, ejecting is probably more likely to succeed in straight and level flight than from a tumbling aircraft. For both reasons, it is desirable to eject quickly once it becomes necessary.
Additionally, a 10 second wait is unnecessary. We see from fighter ejector seats that ejection can be done in just a few seconds. What can possibly be gained by remaining once the seat is ready to eject?
It's a story about a b52 that lost its vertical stabilizer. It flew to the nearest base and landed normally, six hours later at a different base because of wind problems at the first base.
Additionally, a 10 second wait is unnecessary. We see from fighter ejector seats that ejection can be done in just a few seconds. What can possibly be gained by remaining once the seat is ready to eject?