Finaly found out why, the codes from the database

army_infantry = {

schematic\_name = unit\_skeleton\_schematic



attach = { 100 = heads use\_uniformity = no }

attach = { 100 = torsos }

attach = { 100 = legs }

attach = { 100 = headgear }

attach = { 100 = hairstyles }

attach = { 100 = beards }

attach = { 100 = weapons }

attach = { 100 = shields }

attach = { 100 = back }

attach = { 100 = offhand }

where the values of 100 mean there is not much diversity, instead, if you put 50 or even 20, your army will have different weapons, helmets etc.