I realize that we are having fun with this rumor.
As one who has been involved in the certification and continued airworthiness side of the business, my experience is that lots of testing goes on past the roll out, past the first flight and indeed way past the first delivery.
Some of the testing is certification critical and may have to be updated (read completed satisfactorily) before delivery. While other testing (cyclic fatigue) may take some time to accumulate even past delivery.
With that said, its not at all unusual for early results to indicate a design change to be updated in a later ship. Thus the rumor could be true, but the only folks that it really matters are the ordering customers vs their incorporation schedule.
Thus Zzzzzzzzzzz