It's a very minor, but cool touch. Depending on which major ending path you pick for Zion, when you return to Zion from the Mojave there is a subtle difference. If you evacuated Zion, there will be no tribals at all at the Dead Horse and Sorrows camps. But if you crushed the White Legs, all the non-story tribals will still be in both camps, actively walking around, sleeping, training, etc. Little stuff like that definitely makes the roleplaying experience feel more rewarding, since you see the direct results of your choices affect the area.

I crushed the white legs and the sorrows camp is empty.