Mistress Tatjana had an issue with her coach. She felt that he was unfair to her and that he was too hard on her and too critical of her. She had to make him stop that and give her a fair chance like everyone else. That is why she chose to head trample him and ensure that she pumped some sense into his head as she crushed it. He changed.
Mistress Valeria had tried to stomach her argumentative boyfriend but she could not do it anymore. She had to make him stop and since he could not listen to her, she had to use a different method to get it done. The mistress chose to use her head crushing to deal with him. The pain that he felt as she did so made him learn to listen to her and to argue less.