My understanding is that the lore books are written from an in-universe perspective, and the first contains a pretty decent explanation of what does and does not (and did and did not, prior to the seventh umbral calamity) constitute a calamity, as well as knowledge of the ardor, or rejoining.
I think this information is also outdated following our enlightenment on the First, but I think anyone who understands the cycles of calamities will also understand whether or not this qualifies as one.
It would be fun if this scholarly understanding of calamities and the ardor are actually why our friends over at Old Sharlayan are so confident that the world is not ending. I would love to see a story that touches on how academic overconfidence can lead to ignorance.

As for commoners who may or may not even be literate? It would make sense for them to conflate a new type of world-ending phenomena with the one they witnessed less than a decade ago.
But how would those commoners know anything about the aetherial nuances of the calamities?

Plus, who knows? It could be another actual calamity in the making. Even if Fandaniel and Zenos don't care about the ardor, I can't help but wonder what the others are up to.
Perhaps Deudalaphon is still out there, trying to capitalise on this situation.