This seems to be what the documentary is contesting...that they came from somewhere other than Canaan.
The Biblical thesis is that Abraham lived around 1800 BC (using the dating that puts Moses around 1200 and David around 1000), was from the city of Ur in Sumer and eventually traveled to Hebron in Canaan.
We know historically that the population of Sumerian speakers had been in sharp decline in the Ur region for centuries and that Semitic speakers had become the majority. By 1800 the Semitic Amorites were ruling the land and the population was declining as thousands moved north toward Syria because of the exhaustion of the soil and the failure of the barley crops.
It is perfectly plausible that a Semitic-speaking herdsman of Ur around 1800 could and would move from the Ur area to Canaan south of Syria.
No detail of the story is impossible.