That is actually part of it. Understanding 'moods' (for lack of a better term) of sharks is part of the process. The sharks come over on their own. If they don't want to be there, they can always just swim away. No diet is withheld and nothing negative happens if they leave. This animals will always get what they need to live well - regardless of the involvment of the program.
One of the interesting things shark conditioning programs like this have shown us over the years is that sharks seem to be drawn to situations that require thought process (target training, problem solving, handling/interaction etc....). It's also been shown that challenging them mentally with small problems as part of a program leads to healthier animals that tend to live longer.
It's also a HUGE benefit as a keeper to have a shark that is willing to present themselves to you in case of the need for medical attention. (IE: It's much easier to do a physical, shoot an ultrasound, take a weight/measurement, give an injection...).