I think that’s a misreading of the entire book. A black swan event is a rare, high-impact outlier that is nearly impossible to predict under normal circumstances, but is rationalized as having been inevitable in hindsight.
If events like these are "nearly impossible to predict", how come this post is linking to a scientific paper predicting exactly this scenario?
This flood is like The Big One in California. We know it is going to happen, it is virtually a certainty. The only question is when and where.
If glacial floods come as a surprise to you, it is only because you have been deliberately ignoring all the climate change warnings. So, a short recap: we'll see massive droughts, giant wildfires, huge floods due to rainfall, significantly more intense hurricanes, mass starvation due to large-scale crop failure, and low-lying countries drowning due to sea level rise. Oh, and add a high likelihood of the AMOC collapsing triggering a cooldown of the East Coast and Europe to the list.
For whatever reason, you continue to try to ignore the point I'm making, which is that, in terms of natural disasters related to climate in particular, what would have been "rare, high-impact outlier[s]" are increasingly becoming common enough to be not rare and not outliers.