God’s knowledge of what happens in this world “corresponds” (is the best word) to what happens; it does not cause it or even render it certain.
The only way God’s knowledge can be independent of human decisions and actions is if God foreordains them and renders them certain.
Raises an interesting question: Is this a general principle regarding God's knowledge? Does God know how many moons orbit Neptune because x-number of moons orbit Neptune? Is his knowledge contingent on (i.e. caused by, the effect of) the moons in question?
Or does Olson bifurcate God's knowledge of actualities into two different modes: how God knows what free agents will do is different from God's knowledge of trees, insects, inanimate objects, &c.? Is God's knowledge of human decisions dependent on human decisions whereas his knowledge of comets and butterflies is independent of comets and butterflies?