I think their point is that discounting the time estimates is more a constant shifting of the window of what we expect more than them being de-facto incorrect. They’re more off by degree (e.g. an XX% reduction vs complete extinction) than being worthless. As the example points out a large reduction can be very similar to an annihilation it’s just that we are only used to what we know so we constantly shift what is normal.

You have sailed past the point. There were so, so many cod it was hard not to catch a bunch. That isn’t a metric, it’s an indicator that most likely meant vast unseen numbers. The tip of the iceberg is a metaphor for a reason, though it may become an anachronism within our lifetimes.