Wandering zombies?

This was added in 3.11.6.0. However, we rarely see this happen. In fact, I never see this happen. The only time I saw zombies wander around was in that update. Did Nelson remove this feature, or do zombies wander around when we don't know it?

Either way, it'd be nice if he could add it again if he removed it. Or increase the wandering rate if it's already in the game so we can actually see them doing so.