I'm not sure why this never occurred to me before, because it just seems obvious now that I've realized it. Open theists are constantly complaining that classical theism takes its view of God not from the Bible but from Greek philosophers. For a couple reasons why this makes no sense, see this old post. The classical theistic picture of God bears little resemblance to anything the Greeks believed.
What didn't occur to me until just now is that the open theists' picture of God really does bear a striking resemblance to some things the Greek philosophers said. Aristotle, for instance, spends a great deal of time struggling through how there can be true statements about contingent events in the future. On one interpretation, he never solved the problem, but on the most popular view he denies that such statements are even true. It's the latter picture that forms the basis of open theism. Their entire view begins with Aristotle, a Greek philosopher. Alexander of Aphrodisias, a follower of Aristotle, clearly held the view that Aristotle may have held. He doesn't just discuss truth about future contingents but even brings in foreknowledge. He makes it explicit that foreknowledge about future contingents is impossible, so the gods can't have it no matter how perfect they are.