I'm not arguing in favor of the classification system, but, I think if you went to them and framed things as simply as they are here "you require validation every 3 years, we're doing it on every single dive" they would say "that's more than once per 3 years, APPROVED!" so the situation is clearly far more complicated than they are indicating.
Carbon fiber, however, is not known to gradually fail.
James Cameron said it looks like they had dropped their emergency ascent ballast before the implosion, so they may have gotten enough warning to take action. But I would guess that system was never tested to failure in real life.
It will be interesting to see which of the novel innovations supposedly enabling this unconventional design failed, if it can be determined. Rush also lampshaded the fact that his company had "successfully" bonded the titanium endcaps to carbon fiber despite that being contradictory to conventional materials science wisdom, reading the patent for the monitoring system it looks like it may have been intended to provide warning about those bonds failing too.