Some questions about the results of the test set publicized in the paper

Hello, I am very concerned, and thank you for your work. I have some questions about the results of the test set publicized in the paper. Among all the methods, may I ask why the Dice metrics of the left and right eyeballs, left and right optic nerves (and other organs such as parotid glands) differ so much? Is this situation the same in the validation set?