It's more complex than that, but the idea is that a certain personality cluster relates to a specific family of instruments. Wind instruments relate to one kind of temperament while string instruments to another.
Yes, you're right, people need to feel the instrument or there's not much going to happen after all in that relationship with music.
But when you're a child, maybe a guided push from teachers and parents can help you identify what you like instead of going blindly into this amazing universe of musical instruments. Too many options can be overwhelming.