There are several issues at play here. You are right in your intuitive focus - that there is something different about how ancient stories and beliefs are presented in various bodies of ancient literature. To understand what is going on here, I'll initially excerpt a few paragraphs from my [Introduction to Folklore(https://www.amazon.com/Introduction-Folklore-Traditional-Studies-Elsewhere-ebook/dp/B00N65B0BY/ref=la_B001JS9G8Y_1_11?s=books&ie=UTF8&qid=1480337806&sr=1-11):

Something also needs to be said here about myth. People use this term awkwardly. In a European context, myths tend to be the artificial constructs of ancient and Classical-era priests or literate people who sought to weave folk traditions into a comprehensive whole. The exercise often had political purposes, designed to provide diverse people with a single set of beliefs and stories. By reconciling similar traditions, the shared culture of these groups could be seen as more important than the differences, justifying the central rule of the king and his priests. Myth is also a way of organizing and reconciling folk traditions, which by their nature can be contradictory and highly localized. Myth tends, however, to make gods of supernatural beings, giving those powerful entities a status – for modern readers – similar to the Judeo-Christian-Islamic God, even when this comparison is not justified. Of course, it is also important to point out that myths were stories that were told – and then written down – and they were different from religion itself. Many myths were simply the shared cultural inheritance of a group of people.

In general, the word myth is best set aside when discussing more recent folk traditions, recognizing its proper status as a literary genre. Nonetheless, ancient documents recording myths can assist in understanding the history of various stories and beliefs. The authors of these texts were, after all, the first folklorists, and they were the only ones coming close to practicing the craft at the time.

Some folklorists carelessly use the term myth to denote those legends that deal with a fantastic, remote time. This primal era saw the creation of many familiar things such as day and night, fire, animals, people, mountains, and all other aspects of the present world. Folklorists properly refer to these stories as etiological legends explaining the origin of things. Sometimes, however, people interchange etiological legends with the word myth. The problem with this is that “myth” can imply something that is inherently wrong, linked to “primitive” superstitious beliefs. When the term “myth” is used for the folklore of existing cultures or for the traditions that were viable only a generation or more ago, it can take on an insulting, derogatory tone. It is best to reserve the word “myth” for ancient and Classical-era texts.

With this discussion in mind, I think we can focus the answer to your question on the matter of literary presentation rather than the actual nature of the various oral traditions. Although many ancient literary traditions went a long way toward weaving a group of stories into a linear whole, most were satisfied with presenting these stories somewhat in isolation. Centuries of respect for the single written document inspired Hebrew writers to seek to fold in the stories into the various books that make up what Christians call the Old Testament. While these are in themselves separate "books," the effort to arrange them in a linear way and to smooth over awkward transitions allows for the impression that Hebrew tradition was unique.

The various texts of other ancient people are typically presented separately, so they seem less coherent than the Hebrew stories. That said, if we consider what the underlying oral tradition was like, we would almost certainly see diverse, sometimes contradictory stories told by people who didn't necessarily agree with one another but nevertheless shared a common cultural core. And this would have been true of the early Hebrews as much as those of Ancient Greece or elsewhere. The difference is in the means of collecting and manipulating the body of stories in the various oral traditions.