[clueless123]

Yes but,

The author of that fictional book has himself claimed that it is based entirely on fact.

[Borges]

Claiming that hooey is 'based on fact' is an old gambut going back to gothic novels like Horace Walpole's 'The Castle of Otranto'. I believe Brown claimed that 'the conspiracies' were based on fact. And there were indeed such conspiracies. They were false then and they're false now.