If you are quoting VS then the question of oral tradition isn't a question about an Abraham living long before the Israelites. The question is once the Israelites formed and began to unify, after 1000 BCE, did they develop oral stories about a fictive founder, Abraham, OR was this created in 600 BCE when Genesis was created.
There isn't any belief in historical scholarship about any Israelite/Judahite persons before 1200 BCE because they were Canaanites.
Never mind Abraham, Moses is no longer considered to be real as portrayed in scripture.
Abraham looks to be entirely fictional while Moses may be based on a known leader but biblical text is made up. Much of the stories are Egyptian myths from other leaders, also mythic.
Did These Bible Characters Exist? Asking Expert Dr. Joel Baden
3:50 Did Adam exist?
4:15 several different stories about Abraham , don’t line up
5:00 Cain, Able, mythological story
6:07 Enoch, Noah….no, stop, myth
6:44 Abraham exist? Nothing in the Biblical account that we can say is true of any human.
Stories suggest they are regional and each picked a fictive person that God gave the land to.
The stories grew as time went by.
Abraham of Bible, does not exist. An early tribal leader named Abraham, possibly.
9:03 - Abraham is fictional, the character of Abraham is fictional.
9:30 Joseph is a name tied to a region. Tribal connections, story in text is fiction.
10:25 MOSES - nothing in Bible can be historically verified.
Possibly based on a real person who came from Egypt. Maybe helped one slave to become free from Egypt.
Nothing in Bible on Moses is historically verifiable or even plausible.
With Moses there may have been a person named Moses who was some type of leader. Biblical text, all myth.