Consider this, if the groups participating is ranked from 1 to 4th, they will fight in preliminary war against each other; example 1st vs 2nd, 3rd vs 4th which then the victor will fight the victor from 5th to 8th group seed. TLDR version, sometimes for 'a bit' advantage, the group standing in war also matters, why be 2nd only to lose to 1st while when at 6th or 8th place in server; can contend for 2nd place in war.