If the turf is St. Augustine, it could be an application for winter weeds such as Simazine rather than the pre-em. However, since pre will last about 6 weeks (under normal mediuim applications) then getting a kill on early emerging roots would be beneficial on high pressure lawns. On the coast we would use the Simazine in late November-early January since St. Augustine never really goes totally dormant. My own lawn on the coast is almost as green as in October.
We all are merely gleaners from the masters who were here before us.