Let's say a person is upset. Then they sit down and think about their feelings. What if there are two completely different feelings about different things they could think about and get the same catharsis which will have the same effects for the person at the time and going into the future? Then which one was the real feeling?
I think that neither of those feelings are the real one, that the person could choose that they had felt one way or the other and what really matters is the effects of deciding that one has certain "feelings" and deciding in what ways to deal with them. So "feelings" are "real" but they are concepts useful as tools.
Although this LOOKS as if it could, I believe that this is a statement that's trying to be too forward with its thinking. It's similar to saying "Does the existence of a chicken prove a chicken sandwich?" Although the chicken can definitely lead to the possibility of a chicken sandwich, the actual sandwich itself can not only be proven by the chicken thereof.