The kart uniforms, marksmen uniforms and kart helmets in the arsenal are marked as not belonging to a DLC when in fact they are, screenshot.
When playing in-game they are listed as belonging to a DLC and show adverts for the DLC, screenshot.
The arsenal uses configsourceaddonlist in the function it uses to get the DLC.
The return of that command when using kart or marksmen uniforms is,
configsourceaddonlist (configfile >> "CfgWeapons" >> "U_O_FullGhillie_ard") >>> ["A3_Characters_F","A3_Characters_F_Mark"]
The arsenal then uses the first item in the array to get the DLC that the object belongs too. In this case it is getting the base game rather then the marksman DLC.
This is the return when used on an item that is properly listed as under a DLC,
configsourceaddonlist (configfile >> "CfgWeapons" >> "U_O_T_Sniper_F") >>> ["A3_Characters_F_Exp"]
The item version of the uniforms does return the correct output,
configsourceaddonlist (configfile >> "CfgVehicles" >> "Item_U_O_FullGhillie_ard") >>> ["A3_Characters_F_Mark"]