There are a lot of mandatory water maps on the pool which weakens the Cuman bonus. You can invest in fishing ships and navy while the Cuman player will have to either abandon the water or the second tc. Cumans does not have any other eco bonuses so they won’t get a high win rate.
Statistics also say less than half of the victories are conquest which means more than half the statistics come from unranked matches where people can not see other peoples elo so i think the player quality decides the matches there. Cuman or Franks doesn’t matter if a team have a 2000elo player while the rest of the players are just about 1500.
The only statistic i wonder is which ranked maps get the most alt+f4.