The other thing I'd add is unlike D1, where the XC guys are going to run the 5k or 10k exclusively in track, a lot of top D3 cross runners are milers or 800m runners in the spring.
I ran at XC nationals twice, was our 3rd guy one year and 5th guy another, and never ran more than 1500m in track. I could easily break 15:30, but you can't find track results that could back that up.