> We have pretty good documentation on the performance of currencies over the past 500-2000 years.

Not “Pretty good” enough to detect hyperinflation by the definition at issue (50%+ monthly inflation.) Before regular, systematic, and frequent collection of data for price indexes, we have good enough data to make wide-range estimates of inflation over intervals of years to decades, in the best cases, but hyperinflation (whether or not it produces collapse of currency) doesn't continue long enough to show up in that, and also hyperinflation tends to correlate with conditions which reduce the availability and survivability of data. (The author of the article here notes a data problem with Yugoslavia in the late 20th century, for instance.)

In addition to what others have said, we have no shortage of economic collapses throughout history as a result of nations and banks becoming unable to pay their debts and/or basic necessities becoming unaffordable to citizens, we just record them as defaults and bank runs, complete collapses of the entire nations and mass famines (and wars and pogroms to try to make up gold shortfalls) rather than neat little time series of goods prices (which nobody collected in earnest until the late nineteenth century)

> [...] over the past 500-2000 years. It is usually of historical note when an entire nation's economy collapses as a result of hyperinflation.

From the OP:

"[In 2012,] the researchers unearthed a total of 56 episodes of hyperinflation, many of them previously unreported in English-language works."

If we don't even report on the ones in recent high-literacy times, I can't imagine what the odds of this going untranslated/unnoticed are more than two hundred years ago.

"...previously unreported..." "...many of them..."

There is at least a bit of spin in those words that aren't quantified by your impression of them. What is meant by 'many' in this regard? 12 of them (out of 56) were unreported?

Unreported in English-language works, really? Qualify that statement, show me where you or the authors actually combed through all the works of the English language to arrive at such a statement. Show me one example among the 56 for which I cannot find a prior report on in English language works.

Some things are written in such a way as to provide editorial impact. But they're not an accurate representation of the historical record by any means.