At the top levels of chess the identity of the coach/assistant is sometimes kept secret.
What are the advantage(s) of this?
That mystery [second] turned out to be the intensely creative Russian master Daniil Dubov, whose influence on Carlsen would later become clear when he leaned on a specific variation of the Sicilian defense against Caruana.
It seems some advantage is to be gained by surprising an opponent with a variation or opening. Is this correct and are there any other reasons?