The following quotation from William Cunningham about the 17th Century Socinian denial of God's exhaustive foreknowledge, written in the 19th Century, could just as easily have been written about 21st Century open theists. In fact I would go as far as to say that verbally it is very close to descriptions of open theism by contemporary authors. When it comes to error there is often nothing new under the sun.
Cunningham was also sensitive to the positive spin placed on the denial of exhaustive foreknowledge. This is often accompanied, in the writings of advocates of limited divine knowledge, by a parading of the pastoral benefits of open theism.
What appears as great theological insight for today is often found to be the empty soul destroying errors of the past. And that is why good historical theology is an essential part of keeping 21st Century confessional churches healthy.
That they may seem, indeed, not to derogate from God's omniscience, they admit indeed that God knows all things that are knowable; but then they contend that future contingent events, such as the future actions of responsible agents, are not knowable,--do not come within the scope of what may be known, even by an infinite Being; and upon this ground they allege that it is no derogation from the omniscience of God, that He does not, and cannot, know what is not not knowable.
William Cunningham, Historical Theology Vol. 2, p. 173