First of all, I should say that Peter Gentry does not mention or refer to Michael Heiser’s idea that the core thematic message of the bible is contained in Gen. 6.1-4. Peter Gentry’s exegesis, analysis, and solution seek to address this difficult text more by scripture witness than the speculative ideas of Michael Heiser.
When I first heard about Heiser’s ideas about giants (Nephilim), I was intrigued and so I bought a couple of his books. It was not long, however, before the level of speculation and tenuous connections he was seeking to make affected me. What disturbed me the most was that he was shifting the long-held narrative about the bible away from the recognition of Gen. 3.15 as the redemptive kernel. He was saying that Gen. 6.1-4 was the germ idea governing interpretation. This will always fail because it has no solid basis of scriptural reference (recurring motifs which signal theme).
The ministry of Jesus recorded in the Gospels corrects many false notions, both of His disciples and current generation. The correction for the false myths of the 2nd and 3rd century B.C.E. regarding these Nephilim were addressed by Paul in 1Tim. 1.4, 4.7.