Yes, in a way we are always using others as means to an end. But to make this interpretation true, I have to really push the boundaries of what I mean by using others, by mean, and by end.
However, let us try to think this from a different perspective. How about what others in this _experiment_ felt? How would you feel if someone came out of nowhere and asked you to give them this or that when you cannot even fathom why they are doing it?
To me, this so-called therapy may work for the people exposing themselves in order to get exposed to negative reactions. But this is just a very self-centered way of treating other people as cardboard cutouts, not as real persons. They are merely background features like trees, cars or streetlights.
In the end, maybe you get a kick out of getting out of your comfort zone. But you're also training yourself to be indifferent to the feelings of others. If that's the trade-off of this _therapy_, no thank you.