Are we talking about real Europe, or Mythic Europe? In (ArM4) Mythic Europe, there was a lot of inflation in England and Wales around 1200, caused by magi creating piles of silver. In real Europe, there may or may not have been such inflation, but if it did happen, it certainly wasn't caused by magi creating piles of silver.
When I wrote Heirs to Merlin in 1998, the historical texts I used as sources all agreed about the inflation, if they mentioned it at all (it wasn't relevant to all of them). The 2003 article was five years in the future. As a general rule, I don't expect authors for the line to be aware of historical debates that are only available in journal articles, and I give them a lot of leeway to ignore historical debates that have not yet been published when they are writing. Mythic Europe is not real Europe, and while we define it based on careful research into the current historical consensus at the time of writing, it is then defined and stays the same, even if the historical consensus changes. At least until there is a new edition that resets the background.