Except that I argue, as do others - including Jewish sources - that the period between the destruction of Jerusalem and the exodus into Egypt was far longer than 2 months; more likely 4 years. My explanation is at:
http://www.jwstudies.com/Did_Jews_exit_after_two_months.pdf
So the WTS starts from their mythical 537 BCE and say the Jews went into Egypt whenever - no proof either way.
Their problem then lies in the fact that they require the land to be "empty" for the 70 years to run but they wait until long after the first Jews return from Babylon and settle into their towns and villages, then walk to Jerusalem before they end the 70 years. They have no parallel, just a solution looking for a way out.
Their real issue is proving beyond a shadow of a doubt that their ending event is correct (against 2 Chr 36:22) and that they definitely know the year that it happened. No need for neo-Babylonian chronologies.
Doug