See 10507.
God either knows everything or He doesn't.
If He does not, then He is not omniscient. To get out of the dilemma, one has to change the definition of omniscience or of God. Either way, that gives us a different God than we had before we changed definitions.
It's not the definition of omniscient that's the error. It's equating it with double predestination.
That takes two more steps.