It was a normal filing online with no intentional expedite. We filled under the 3 year rule.
As the previous reply impressively predicted, my husband is in the military. However, we never requested it to be expedited nor made a specific mention of his military affiliation. For what's its worth, when I had my infopass appointment, the officer looked up my I-751 and it was not even at the local office yet. 2 weeks later, we got the dual 751 and n400 interview notification.
Whatever happened, we are incredibly appreciative for the quick interview.