There's a crucial difference between a complex system and degrees of freedom. For example, a modern airliner is a very complex system and these days it's not possible to predict the precise behavior of autopilot systems under all circumstances.

Does this mean those systems have "free will?"

Of course not. The problem is, we haven't defined what we mean by "free will." Is it a binary thing, where one either has it or does not have it? Or can people have some small degree of free will (choice of thought or action) in a limited range of circumstances? The latter seems far more likely.

If we want to flap our arms and ascend into the air, does "free will" ensure we can do so? Obviously not. As we are hardwired by hundreds of thousands of years to behave in certain ways, because those behaviors were on average beneficial, we are just as constrained in our thoughts as we are in our actions due to the physiology of our bodies.

It is always more useful to think carefully about vague abstractions than to fall into the trap of attempting to talk about undefined entities and thereby ending up either with specious nonsense or vacuous ramblings.