The reasoning for the rejection is largely foolish. For instance, the NCAA writes:
"With the current race distances for men and the current race distances for women, you have similar amounts of competition time spent running per gender."
Women finish at the D1 level in 19:27 to on the order of 21-22, whereas men finish close to 29-32. If women ran 10k, the times would be on the order of 32-37, which is closer than the current difference.
The competition committee also points out in their defense that the men and women use different implements, have different hurdle heights, "etc." But they pass over in silence the fact that men and women now run exactly the same distance on the track for every non-multis event except for the 100/110 hurdles. Specifically, they both run 5000m and 10000m. The only real drawback to moving the women's race from 6k to 10k is that you'd lose some of the shorter distance runners, but that's already happened for the men. A way to resolve that problem--especially to get more 800m runners in xc--would be to have a short course (4k or 5k) race like they used to at World's. However, that would split up the competition or lengthen the # of days at NCAA champs.
Lastly, the reasoning involving finish line spread isn't an issue for the men at 8k--not that I favor reducing the champs length--if it were, they wouldn't run 8k all season long until regionals.