I tend to arrive amply early and I recall doing that flight and being held outside the entrance to preclearance until officers arrived for their shift, and also, I believe, being unable to get up to the MLL because it wasn't open yet, and post security, standing in a growing crowd for the MLL elevator (all of whom thought they uniquely would be able to make the elevator go).
Unfortunately I did not take note of the times that either logjam cleared.