It was a 5k, but MileSplit has designated it a 3.0, just like they did McNeil this year and Region 1A-6A last year.
I just did a Google path on the exact course and it came in at 3.07. It honestly doesn't matter much, what will matter is placement at State. Coaches recruiting will always want to see the complete body of work a runner has and Southlake does its runners good by having the track 5000 Spring Break so you take the distance/hard course/easy course variables out from the usual XC time analysis.