[ElBorrachoInfamoso]

I checked out that link. That quote is speaking more to relativity independent of whether your perception of the timing of events has any real impact on your free will.

Even within a relativistic universe, it is possible to construct a thought experiment in which an external observer can see everything that is happening "when" it is truly happening. Of course such an observer would have godlike powers.

For those of us in the universe, relativity just tells us that our perception of when things happen depends on our position and velocity over the entire time period from when the event actually happened to when the light from the event reached our eyes (or sensors).

Relativity does not say that our future has already happened. It says that things we will perceive as happening in the future have already happened. The godlike observer I mentioned before would have seen the thing when it actually happened and even we have developed theories that are good enough to correct for the error. So you may see the light from a star tonight, but you can calculate when that light was actually emitted.