I was referencing a direct quote from the author, looks like the Booker Prize board actually looked into it and disputes the certainty of the claim. Oh well. However:

1. Regime change doesn't happen instantaneously. The Francoist line of thinking was still pervasive after Franco died, and through the 70s there was a waxing and waning of censorship.

2. The book was still restricted in multiple states, the spirit of my comment still stands.