Well, of course God can think of things without their becoming reality, like how God knows of a reality where sinners would freely repent who don't in this reality.
But, that is evasive and you know it. What did God have a vision of, something He observed or something He created?
None of it existed at the time he saw it. He chose for it to become reality and he then set it in motion. AND he maintains it and has the power to answer PRAYER....that changes things.
Unless you don't believe that prayer changes things.