I favor the idea of free will but I don't buy this argument. Everything in the universe is bound by the same physics/quantum mechanics but you wouldn't say a rock has free will.
To me, free will implies choice. I don't see how non-determinism is equivalent to choice. I can see it as necessary but not sufficient. I do not see how the "free will theorem" shows that elementary particles are choosing their spin. It seems that they mean free will differently than I do.
>It seems that they mean free will differently than I do.
No, they mean it the same way you do; they only made it precise.
You probably suppose a scientist doing an experiment can choose between A and B for some setup. If so, then so can particles, because one can make experiments where a physicist can make a choice affecting the outcomes, and the particles in the experiment can choose their behavior in exactly the same manner.
So, since there are experiments that allow you to "choose" freely, and such experiments have particles able to do whatever you are doing, then either your free will implies their free will, or neither has free will.
Follow the links from the wiki page to learn more. It's quite precise, and is exactly the usual concept of free will.
Thus if you want to have free will, then so does a rock.
[1] https://en.wikipedia.org/wiki/Free_will_theorem