Why three teams works
Three teams keeps everyone active without the boredom of long benches. In sports, a three-team rotation lets one side referee or rest while two play. In workshops, three groups produce enough variety to compare ideas without the chaos of five or six. With odd group sizes the tool will distribute leftovers one-by-one — you'll get teams of 4-4-3 from 11 people, never 5-5-1.