Understanding JSON object mesh.

I am exploring the possibility of writing a plugin to export Blender scenes to tabletop simulator and therefore I am trying to understand the JSON format of workshop mods. Take for example "GO (Small 9x9 Board)". It's JSON file lists the following object under "ObjectStates":

 {
      "Name": "go_game_bowl_black",
      "Transform": {
        "posX": 12.6353416,
        "posY": 0.5687232,
        "posZ": -12.0988655,
        "rotX": -2.0712012E-05,
        "rotY": 3.40778136,
        "rotZ": 8.576248E-06,
        "scaleX": 1.5,
        "scaleY": 1.5,
        "scaleZ": 1.5
      },
      "Nickname": "",
      "Description": "",
      "ColorDiffuse": {
        "r": 0.9191252,
        "g": 0.87308,
        "b": 0.7907293
      },
      "Locked": true,
      "Grid": true,
      "Snap": true,
      "IgnoreFoW": false,
      "Autoraise": true,
      "Sticky": true,
      "Tooltip": true,
      "GridProjection": false,
      "MaterialIndex": -1,
      "MeshIndex": -1,  
      "Number": 99,
      "XmlUI": "",
      "LuaScript": "",
      "LuaScriptState": "",
      "GUID": "56bf16"
    },

I can't see any reference to a mesh file other than MeshIndex: -1. In some other mods I see "CustomMesh" which contains a link to a "MeshURL" and that I understand. But what is happening in this Go game? How does TTS know which mesh to load for this object and where to get the .obj or vertices? Could it be that this object is included in the assets of the game and as such the -1 in the meshIndex tells TTS to look inside its already existing assets and find the mesh by name?