If God were a man, you might have a point.Prognōsis (4268) literally means "before knowledge" and refers to knowledge acquired in the past being utilized in the present and never refers to future knowledge.
In Acts 2:23 Jesus is put to death by the previously declared plan and being implemented in the present by God.
In 1 Peter 1:1-2 people were chosen according to God's redemption plan method, being implemented in the present,
If you care to study the actual concept, you can also look at the related "verb" form of the Greek word, found at Acts 26:5, Romans 8:29, Romans 11:2, 1 Peter 1:20 and 2 Peter 3:17.
In every case an action to be taken in the present is based on prior knowledge of the past.
Study and learn.