When mistress Gaia noticed that this slave was full of shit, she had to make sure he learned to eat what he was full of. That is how the slave found himself being given tutorials of how to eat shit. And at first he thought she was joking. But he realized she was not when she actually made him practically do what she had told him to do a little earlier.
Mistress Wael wanted to teach this guy not to take her for granted or to mess with her. And that is why she chose to crush his nuts with her hands to make him feel the pain and also learn to obey her. The mistress then made him eat her shit and drink her pee. He did not say a thing as he was afraid of having his nuts crushed again.