Boyd explains why foreknowledge actualizes an event. From Reknew:
EDF [exhaustive definite foreknowledge] and Actual Occurrences
P1) If God possesses EDF, the definiteness of all events eternally precedes their actual occurrence.
P2) Actuality is distinct from possibility in that actuality is characterized by definiteness, while possibility is characterized by indefiniteness.
P3) Thus, all events are actual before they are actual.
Conclusion: It is absurd to say that an event is actual before it is actual, thus (reductio ad absurdem) God does not possess EDF.
Comment: This argument raises the question, What does the actual occurrence of x add to God’s foreknowledge of x so as to distinguish the actual occurrence of x from the mere foreknowledge of x? If God’s experience of the actual occurrence adds anything to God’s foreknowledge, then God’s foreknowledge cannot be exhaustively definite. God learned what it was to experience x even if we concede that prior to this God had perfect propositional knowledge about x. If God’s experience of the actual occurrence of x adds nothing to God’s knowledge, however, then it becomes utterly impossible to render intelligible the distinction between a thing’s actual “occurrence” and its being “merely” foreknown.
In other words, if experience is the highest form of knowledge (and it most certainly is), then an exhaustively definite knowledge of x entails an unsurpassably perfect experience of x. Hence too, an exhaustively definite foreknowledge of x must entail an unsurpassably definite experience of x an eternity before x occurs.
To salvage EDF, then, we must either grant retroactive causation or grant divine timelessness. Whether these concepts are either philosophically or biblically defensible is questionable.