If you were to rewind time and watch the flip of a coin over and over would you expect the results to change or to stay the same?
As for this proving no free will one way or the other. How does someone choosing to make the same decision in a certain set of circumstances mean it wasn't free will. Some decisions are easy for people and many things would need to change to change the persons mind.
While if the decisions were different could mean it's a harder decision or just a less committed one. I don't see how you can just dismissed it as random though. Seems like you are oversimplifying to make a point.
If you rule out all free will as predetermined or random. You clearly think that free will doesn't exist and will argue any way to say so. So I'm curious do you feel you were predetermined to come to that conclusion or do you feel you came to it randomly? If your response to this destined to happen? Or will it just be from random happenings?