Yes , I understand , your probably right , if they had loaded it wrong they would have learned the hard way , I have seen many period photo's where the troop seat were left on and the partition not used as in the book "The GMC Universal truck " by Boniface & Jeudy in an effort to increase the load carried......
The idea for those who don't know was to have the load self limited by the low sides of the dump body , ie you could only pile so much on the truck before gravity would cause it to slide off known as the angle of repose , if troop seats or side extensions are used yes you can put more on but it will be/can be more than the hoist or truck chassis can support.
There is no hoist frame past the partition just the heavy gauge steel of the sides and one central rib that runs from the partition hinge to the end of the body.
The CCKW 353 H1 or H2 split / banjo was a multi-purpose truck able to do many things , it was an ok dump truck and an ok cargo truck , not is the same league as the much beefer purpose built Diamond T dump truck.