More confirmation bias than fabrication I think.

He knew that legendary players such as Capablanca and Kasparov had understood the game — he clicks his fingers — “just like that.”

Imagine that, within five years, people have become firmly convinced of your genius — by whatever means: the next great American novel, solving the twin prime conjecture, overturning physics, etc.

How long do you think it would be before your parents, the media, etc. started telling anecdotes about how prodigiously gifted you were as a child, understanding in a flash, that they always knew you’d be brilliant?

All the stories about Capablanca, Kasparov, Gauss, and so on are, if not complete fabrications, mostly false.