Like all of the Watch Tower Society's extra-biblical speculation this too is utter nonsense, or as others here have observed B.S.. Such speculations are an attempt to make ridiculous myths/folktales seem "logical". A straight unassisted reading of the Bible without having preconcieved apologetics in mind will reveal a simple collection of tall-tales which are as obviously untrue/nonliteral as any other religion's/culture's folklore. The Watch Tower Society's speculations on the Bible are akin to trying to make a literal story out of Jack and the Beanstock by explaing that ancient bean plants were much larger and could be climbed to observe antigravity castles in the clouds.
One obvious example is the Cain story from early Genesis. If Cain and his most intimate family were the only people in the world why did God give him a mark so people would not kill him for his crimes against Able? If Adam, Eve, and Cain's brothers and sisters are the earth's only inhabitants, then surely it is easier for God to just tell them not to kill him without some mark to interpret and even if there were further removed nieces and nephews how would they know how to interpret such a mark anyway? It is clear that such a mark was intended for far-flung strangers since Cain was punished by becoming a vagabond, how a stranger would know what the mark meant or how they would hear of the crime we are never told. It seems the teller of this tale had every expectation that there were other people scattered about the world besides Adam, Eve, and their family and hence why it is so easy for Cain to find a wive in his vagabond travals and eventually finds enough people to found a city. Founding a city, by the way, is the exact opposit of being a vagabond so God's punishment/prophecy is easily and inexplicably thwarted.
One last clue that this story is complete nonsense is the fact that God throughout the rest of the Bible is so forceful in punishing murder (and other lesser crimes) with death and yet Cain gets away with just a mark. Complete nonsense.
Other quick examples come to mind, especially the 70 + year old Sarah being so desirable for an Egyptian king's harem and then having the story repeated again when she is 90+ years old with another king. How desirable could she be at 70 or 90? Especially since she died of old age around 120+ years old so saying she aged at a slower rate doesn't make a good explaination since even subtracting 30 years from her real age still makes her 40 and 60 and no matter how beautiful she was how she could she possibly compare with girls 15 to 25 which would be easily available to a king? It is also explained that she was so aged and barren as to make a miracle from the birth of her son.
The treatment of Hagar and Ishmael by the wealthy Abraham also makes no sense because they are exiled into the desert with only a flask of water and a loaf of bread when Abraham could have afforded to send his son out with flocks and servants and plenty of food. Death was not God's plan for Ishmael since He provided another miracle to save them so why not just equip your son with a tiny portion of your wealth and send him on his way?
