I would explain it as the difference between knowing and feeling.
Think about it like this; everybody knows how to lose weight, balance between eating and activity. Yet how many people know this but do not feel motivated to embrace a healthy lifestyle?
Sports psychology examines how the mind impacts performance. For example, you may examine; when I am nervous how does that affect my performance? I suspect most people already know the answer.
In hypnosis you engage directly with the subconscious mind. So not only do you learn how your mind is impacting your performance but you also change your belief and expectation at a much deeper level. This creates a fundamental shift in how you feel in the lead up to and during competition.