This is a limitation of the scope of science, not a "bias" specifically of the theory of evolution.
It was unclear to me that the bias referred to how the theory came about, versus a bias inherent in the theory itself. I assumed the former.
Regardless, some scientists have no qualms about ignoring the alleged "limitations of the scope of science" when it doesn't disrupt their worldview; for example, the multiverse concept - hypothesizing about untestable and unobservable "other" universes outside of our own, as a way of proposing how a just-right-for-life universe could randomly come about. Sounds a tad metaphysical to me.
Evolution must explain all human behaviors and the outcomes of those behaviors.
Do you have evidence that it does not?
ALL behaviors are the product of, and allegedly explainable by, physical processes, there is no such thing as true free will. We are all, as Pearcey states in her book Total Truth, machines made out of meat.
Please justify this claim with evidence.
I'm not quite sure where you stand here. Do you think evolution explains all human behavior, or do you think we are NOT purely physical beings? If the former, please give me your definition of free will and I'll be more than happy to go from there and address the inadequacy of a materialist, evolutionary view to explain the origin and existence of free will.