What is the fruit of One Piece?

Rox is a secret fruit. On this premise, we have the following two speculations about the secret fruit of the fourth captain of the White Regiment, Saatchi:

First, the white beard group didn't know it was a secret fruit, only the black beard knew it.

Second, the white beard group knows it is a secret fruit, but it doesn't know the specific ability.

In the first case, Ace's ignorance of Blackbeard is justified. Blackbeard didn't know it was a secret fruit, so he didn't give some reasonable advice to Ace. Paradoxically, when Black Beard appeared in the peak war, White Beard used his ability to fight against it for the first time. Obviously, White Beard doesn't understand the ability to secretly result, which is contrary to our hypothesis.

White beard was not the only one who unlocked the lock at the scene of the war. The Warring States, Karp and Crane all competed with the lock on the world stage. However, judging from their reaction to seeing Blackbeard, they didn't show the shock and suspicion they deserved, which also showed that they had never seen the ability to steal fruit, and indirectly proved that Locks was not the ability to steal fruit.