.Charles,
that is good to point out what this is. I will say that I had never heard of the term until within the last year and have debated the issue with several.
Also let me say that your description is true as far as it goes, but there is more to it then what you mentioned. Also there is no real set in stone standard for this belief system. Some go further then others. You basically stated what they believe, but they do not believe that way to limit God. They accept that He does know certain things at certain times even in the future. The bible does show us that He does. Yet because it seems like he does not always know all things then He most likely limits His foreknowledge. One example that is given is when God says It repenteth Him that He ever created men. The idea is that if He absolutely knew how far men would go ahead of time and then created them any way and then says that He regretted creating them it makes no sense.
So they hold that yes He knew that men would fall, and needed a Savior, and He knew how far men could go, but did not know they would go as far as they have since He limited his knowledge to keep thigs as pure as possible..
An earthly example is that when we have children we all know that they will sin against us. And we all know how far that sin can go, but we do not know how far each one will take it. One might just not carry out our wishes like we would like. Another might talk back and swear at us while another might beat us and murder us. We know it could happen, we just do not know it will. In the case if God some times He may be able to know all, but limits Himself to certain things. Thus coming up with what is termed open theism.
They can have some difficult arguments. They also point out that if God knows every event in all history and history cannot be changed outside what is set since He already knows what will happen then who set history in stone. Does God look down through History and see what would happen. If so then that means there was a time when He did not and that history is an entity in itself. Or did God decide what history would be like controlling it all Himself? I think we all can see the problem there. So some of what they believe is difficult to answer, but like you I do not believe that we can even hint that they are lost because of this belief.