I'm not on a hiring committee but have plenty of interview experience at FB. Biggest determinant of level on offer is how you do on the design/architecture interview but who knows.
Honestly I would walk away unless they give you E5+. I know several good engineers that were misleveled at hire. They got immediately promoted the next performance cycle, but they missed out on the RSUs they would have had if their initial offers were leveled properly, and that's serious money.