It's not what God knows. It's God knowing them. It happens to the individual. There is a spiritual reality to this knowing. It is not intellectual knowledge. It is spiritual in nature. An example is found in Romans 8:15-16.Of course they can't perform the second knowing because that is what God knows. You have to be God for that!
But that was not what we were discussing. We were discussing what men know so get on topic please.
This is what is lacking in those in Matthew 7:21-23. Jesus never came to those individuals in this way.