Auld Soul
Your query is an interesting one but completely mistaken because WT chronology as developed by celebrated WT scholars, hereafter termed the 'celebrated' have based their biblical chronology on the historic fact of the biblical 'seventy years' which is overlooked by Neo-Babylonian chronology. This means that the dates for the reign of Nebuchadnezzer is dated from 624 - 582 BCE with the desolating of Jerusalem and the commencement of the seventy years in 607 BCE which was his 18th regnal year. Such an historic insertion unknown to the pagan Babylonian scribes would create a twenty year gap between biblical chronology and pagan chronology which fixes 586/587 for this event.
Further, the chronology for the following Babylonian rulers in uncertain because in the case of Evil-Merodach there is ambiguity as to the length of his reign whether it was two years or eighteen years however his reign began in 581 BCE and in 580 BCE released Jehoiachin in his 37th year of exile which commenced in 617 BCE. Following from Amel-Marduk' uncertain reign there were the following kings: Neriglisser, Labashi-Marduk and Nabonidus who began his reign in 556 BCE ending in 539 BCE.
The Neo-Babylonian chronology is unreliable because it does not give an accurate history of the Nebuchadnezzer period and bad history equals bad chronology. The following historical facts are missing from the Babylonian period but are mentioned in the Old Testament writings:
1. The seventy years of Judah's subjugation
2. The seven years of Nebuchadnezzer's madness
3. The desolation of Egypt for forty years.
Hence, the missing twenty years is not found during the late Neo-Babylonian period as you allege but in fact were characteristic of Nebuchadnezzer's reign with the Fall of Jerusalem in his 18th regnal year.
scholar JW