Because it is not a "when" issue.
Matt 7:21-23 Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity.
Is Jesus Christ, the Son of God, claiming He has no knowledge of them? I thought God knew everything. Therefore, it is foolish to take the idiom "to know" in the case of God's relationship to man, and make it an intellectual exercise. To "know" mean "to love".
Interesting passage in light of "ye that work iniquity":
Ps 5:5 The foolish shall not stand in thy sight: thou hatest all workers of iniquity.
So when you have the phrase "Adam knew his wife Eve" and you have Christ knowing His bride the true church and you juxtapose that to the "workers of iniquity", and we have God hating "doers of iniquity", then you have the proper thesis-antithesis of love/hate (no gray zones) in God's relationship with His elect and God's non-existant relationship with the vessels of Wrath.
Jacob I loved, and Esau I hated.