As an Oranje supporter who hated the Argentine regime and thought the tournament shouldn’t have been played there (i.e., like Kuper in all respects), I’ve always tended to give some credence to the claims, but you are of course right that we are almost certain never to know the truth.

Failing to provide any evidence of a motive (at least in the radio version) is obviously the weakspot of Mondragon’s story. One also wonders why he didn’t include such a blockbuster in El Hijo Del Ajedrecista 1 (unless he had a multi-book deal from the beginning).