The confusion arises because technically there should not have been any Nephilim surviving the world wide flood of Noah. So how was it possible for them to cross over into the new world? This in reverse attempts to dismantle the heavenly hosts copulating with human women because there was never a second incursion after the flood. So therefore if there were Nephilim post flood without an incursion then the first Nephilim a must have been fathered by humans pre flood just like post flood. But that’s a simplistic and incorrect conclusion.
This subject is far more complex and nuanced. A simple answer will be picked apart, requiring the whole picture to be painted.
Nephilim were the great men of old. Even the Bible calls them men v4 אנשׁי of renown.
They are men in that their mothers were human women. Their fathers who raped their mothers were heavenly beings. Heavenly beings were not intended to marry. Jesus says as much in Matthew 22:30. They were never given a female counterpart. But that doesn’t preclude them from being capable of procreation
Adam who is also called a son of God, made a little lower than the heavenly beings psalm 8, was given a female counterpart and told to procreate.
The heavenly beings curious as they were, also called sons of God or Benei ha’Elohim, are also called Watchers, observed the ways of men and without going into their motivation for their actions, a select number of them decided to abandon their abode, raped the human women, impregnating them.
The obvious question then becomes how is that possible? Is it possible?
“I will put enmity between you and the woman, and between your offspring and her offspring; he shall bruise your head, and you shall bruise his heel.””
It is clear that whoever this being was, could have offsprings. We just read as much.
“And the great dragon was thrown down, that ancient serpent, who is called the devil and Satan, the deceiver of the whole world—he was thrown down to the earth, and his angels were thrown down with him.”
Revelation identifies him as satan or deceiver, and we know him to be a heavenly being. We can extrapolate that heavenly beings are capable of procreation because Gen3:15 speaks of their seed or their offspring in a more modern interpretation.
We understand that Genesis 6 claims that ALL creation had been corrupted EXCEPT for Noah and his family who were Tamaiym or pure or untainted. However the three sons ended up taking three wives (one each) and these were not referred to as pure. Their tainted genome crossed over from the old world destroyed by the flood into the new world through Noah’s grandchild Canaan who Noah curses for Ham’s actions. Which means Ham did something out of desperation due to Canaan his son, Noah’s grandchild. Otherwise Noah ought to have cursed Ham.
Canaan’s lineage would actively select to procreate and select for the Nephilim phenotypes. They also happen to concentrate in Shem’s geographically assigned region rather than Ham’s geographic portion, because the land of Israel was situated here, possibly the location of the garden of Eden. These Canaanite’s had Nephilim blood and the sons of Anak, who descended from Canaan the grandchild of Noah, had a very strong expression of their genes, especially known for their size.
Goliath was a dwarf in comparison to a true Nephilim.
““Yet it was I who destroyed the Amorite before them, whose height was like the height of the cedars and who was as strong as the oaks; I destroyed his fruit above and his roots beneath.”
Cedars don’t grow to 7 feet tall, a small cedar grows at least 25ft tall.
Are Nephilim men? In a sense yes, because they were halflings, part human. They certainly had the phenotypes of men and were generally indistinguishable from men except for their Nephilim features, be it height, extra digits 1 Chron20:6, elongated skulls, animal fur covered bodies Gen27:16 or other distinguishing feature.
They are not fully human per se. Which is why some would not consider them human and are categorized in their own separate grouping the Nephilim or the halflings. Remnants of the their genetics still exist today. Passed through the mother they could have been eliminated entirely from the gene pool. But deliberate selection kept them in the human gene pool.