Grid mod is official feature of the game now, that is the true difference. But nonetheless it is a global feature that spreads across the entire map without interaction with objects. Small tree mod is super local and changes just the appearance of the object itself on the same tile it is existing. Tower range mod is something in between. When there are mods that introduce a switch where you can toggle on a map vision mode where the surrounding terrain of a tc in 30 tile range is highlighted (in super intese purple) to show holes in between objects, it would get the same criticism since it more than just changing the graphics of the object itself on the tiles the object is standing.While I agree that the argumentation was pretty fuzzy, I have to agree with RobChang that there is a difference between changing the visuals of an object and adding stuff around it. The small tree mod changes the tree visuals on their spot (1×1 tile). So does the cube mod. The grid mod is a bit of a special case but from my perpsective it should be possible to see the map with all details incl. where tiles end, so it kinda feels like fixing a visual bug to me.
It is not about the definition (the judical definition is still to be found) but the intent of actually helping in playing the game are not covered by allowing all kind of visual mods which for me reads as object asset replacements but only the objects themselves. That is why I want clearer rules if tournament host want to prevent such external help to be used and the game to stay more vanilla.