for the most part, the double mag-pouch came about during the GWoT, it has its purposes. it frees up more space for other things on the soldier's vest, for example med kit as you provided in the pictures. it also doubles the amount of ammo you carry on a patrol, giving it an edge during sustained firefights. and my fav thing about them is that you can rest your rifle on the pouches during patrol.Based at the location of the smart tablet the pouches clearly located in the center of the vest like this
Us soldiers also wear bulky double mag pouches
looking at the pics though I am not sure those guys would be too happy laying in prone with those vests, or crawling.