"Cards speak" means that any verbal declaration as to the content of a player’s hand is not binding.
Likewise if John says he has a flush, but in fact he does not, his hand is judged on its actual merits, not his verbal declaration.
[4] At the discretion of management, a player deemed to be deliberately miscalling his hand may incur a penalty.
[5] The "cards speak" rule does not address the awarding of a pot, player responsibilities, or the similar one player to a hand rule.
It merely means that verbal statements do not make a hand value, but the cards do.