I think the writer is stretching semantics and may be looking for arguments.

The reality would be that Christ was the Lamb slain before the foundation of the world. Revelation 13:8 occurring some time before Genesis 3:15

The simple fact is that from before Creation God put in place a plan for the salvation of mankind. He knew Adam would sin and fall, and thus the immutable position arose - the wages of sin is death.

God could not just excuse Adam's sin and the sinner had to die - no other way. So He showed us the way, from the death of an animal (probably a lamb) of Genesis 3:21 since the Lamb is the continuing Biblical theme. Behold the Lamb of God who takes away the sins of the world.

The passage of time since Genesis 3:15 we see the outworking of God's plan for the redemption of His beloved creation - mankind.

The reality is we are Yahwehs' and always have been. He has worked in many ways through many people but always to achieve His plan - which will not fail no matter how we - making - screw it up! The opening verses of John's gospel and the books of Hebrews and Revelation say all we need.