Eve is about balance. It trains you to perform a correct pull up by making you more aware of your balance and force. Hanging on the bar, you become aware of yourself, to pull up, you must be balanced and lift yourself evenly. The arch form will support your weight when you pull up evenly, however, favor one side or the other and it will not allow you to continue.
Additionally, eve can be stored/displayed on the wall as sculpture versus the typical eyesore of exercise equipment.