That is a lie, I had a fight once recently with 3 level 4 Footmen the enemies where numerous enough that they all got really low on health. One Footman had 3 spirit at about 1/3 health left he started doing the run away attack that the scared guys do, One Footman had 5 spirit at about 1/4 or just under 1/4 health he started doing the same thing, the last Footman had 6 spirit he was almost dead before he started exhibiting that behavior. So unless you always have a large army such that your troops never fall below 1/2 health spirit will effect you in every fight you do.