It is strange for a paper to claim free will can or does exist without defining exactly what free will is. If free will does not need a formal definition because it is self-evident, then its existence must also be self-evident. But I propose that free will is best defined in the context of psychology and neurology rather than physics and mathematics. I will give a practical example to show what free will is as commonly understood by the general population.
A person killed a victim. Is it murder or homicide? Since the latter carries a less severe punishment, the defense lawyer will try to prove it is homicide. One way is to prove that the person is insane. This will require many psychiatric tests and records of past tests that show the same result. What do these tests mean? The person cannot exercise free will because of mental disability.
From this example I give an operational definition of free will - human actions borne out of conscious and rational mental processes. Physicists immediately see a problem here. Molecules in the human brain cannot distinguish between conscious vs. subconscious, rational vs. irrational mental processes. (What color is bitter? It's a wrong question.) This is the futility of trying to explain free will in terms of elementary particles, reductionism and determinism. Despite this glaring contradiction, physicists nonetheless talk about free will without regard of how psychologists define it. It only proves that when physicists say free will, they must mean something else.
Physicists cannot explain how rational thoughts and consciousness can arise. This does not nullify the observations of rational thinking and consciousness by psychologists and neurologists. A chimp looking at the moon is perpetually puzzled what it is and how it came to be. Not knowing the answer to these deep questions, the chimp concluded the moon does not exist. How free will can arise in the human brain is a deep question. A not so deep question is why some physicists insist free will does not exist. My answer to the first is unknown. My answer to the second is chimp brain.