This is partly explained in the appendix to the article that you’re reading:

“Preindustrial England has a uniquely well-documented wage and price history. The stability of English institutions after 1066 and the early development of monetary exchange allowed a large number of documents with wages and prices to survive,” (Clark, pg. 1321)

England was a relatively “small” place. That is, it was pretty big, geographically, not really that much smaller than say, France or Spain or Germany or Italy, but it was relatively compact, since it’s on an island. Like other medieval kingdoms, there were places on the periphery that were culturally/linguistically different (Wales and Scotland), but unlike kingdoms on the continent, the authority of the king extended over a fairly well-defined area. For example in France, the king controlled Paris and the surrounding area, but the further you travelled from Paris, the less power the king had, and eventually you’d be in a place where the king had little or no authority at all - Toulouse, Aquitaine, Champagne, Flanders, Brittany, etc. And some parts of France were actually controlled by the English king, to make it even more confusing. Spain had several kingdoms that weren’t legally united until the 18th century, and Germany and Italy were filled with numerous smaller states and weren’t united into single countries until the 19th century.

So, part of the answer is that England, at least after the Norman Conquest in 1066, happened to develop a centralized authority with a king recognized by the entire, relatively well-defined and compact country. It was easier to develop a top-down, centralized economic and legal system. It’s not a small place but being on an island, it’s sort of a “small world”. (Note that places in France ruled by the English don’t have the same amount of surviving sources - they weren’t really part of England, they were territories of the king but in his capacity as Duke of Normandy or Count of Poitou or wherever else.)

That is not to say that kingdoms on the continent had no archives at all. Once the kings of France established control over all of France, they adopted a centralized administration, like the English had. There were archives of information that would have been extremely useful for historians. As an island, it was also easier for England to escape the destruction of wars and revolutions. A lot of the sources and documents that would have been useful for historians of medieval France were destroyed during the Wars of Religion in the 16th century or especially the Revolution in the 18th century. Similarly for Germany, there was massive destruction during the Thirty Years’ War in the 17th century.

World War II was also pretty destructive. In Italy there were archives for the Kingdom of Naples, which covered the southern half of the peninsula and Sicily, if not the whole country. But those archives were destroyed by the Nazis during the war. Both Italians and Germans tried to save them but one Nazi commander burned them anyway, apparently purely out of spite.

England did go through wars and revolutions of its own - the Barons’ War, the Peasants Revolt, the Wars of the Roses and the Glorious Revolution, they were all pretty destructive too. During the Reformation in the 16th century, some destruction occurred during the Dissolution of the Monasteries. But none of these were as destructive as wars on the continent, and it helped that England already had a centralized government and administration before all of that happened.

So, short answer - England had a more centralized government, which was easier to establish on an island; and, when similar archives did exist on the continent, they were often destroyed by violence that England was able to avoid.

Sources:

Gregory Clark, “The Condition of the Working Class in England, 1209–2004”, in Journal of Political Economy vol. 113, No. 6 (December 2005), pp. 1307-1340 (the article quoted in the question)

Jean Dunbabin, France in the Making, 843-1180 (Oxford University Press, 1985)

Richard Mortimer, Angevin England, 1154-1258 (Blackwell, 1994)

Which period?