I summarized R. Eleazar Ashkenazi’s position in his Tzafnat Paneah, pp. 29-30, as follows:
He also offers another explanation for the lengthy lifespans [in the Torah], namely, that the Torah recorded what the popular belief was, no matter how exaggerated, and Moses was not concerned about these sorts of things. In other words, just like today people say that the Torah is not interested in a scientific presentation of how the world was created, R. Eleazar’s position is that the Torah is not interested in a historically accurate presentation.
…Ashkenazi’s viewpoint is interesting because he acknowledges that in certain factual matters the Torah is not exact, and indeed this is not a concern of the Torah. This sounds very similar to how many people explain the first few chapters of Genesis. Yet it is much less common for Orthodox spokesmen to extend this approach to later chapters of the Torah, e.g., to say that say the genealogies recorded are not accurate. But is there a conceptual difference between saying that the Torah is not interested in presenting creation in a historically accurate form, and that is why there is no mention of billons of years or of evolution, and saying that the Torah is not interested in exact genealogies, but simply presents what was commonly thought and this explains the lengthy lifespans? If there is no conceptual difference, where does one draw the line? Surely there are some parts of the Torah in which factual history must be assumed. This is an issue that has not yet been adequately dealt with, and I will soon be publishing a letter by a great Torah scholar which refers to this problem.