Mue I might phrased it bit misleadingly but I think the engine populates the tiles with the TOD objects on the fly when the scene limits allow so -the terrains in the old pre NA format have statements about the maximum numbers of possible TOD objects spawned around player in the terrqain's _DATA.INI: example here:
SolidObjectVertexCount=12288 SolidObjectIndexCount=18432 AlphaObjectVertexCount=8192 AlphaObjectIndexCount=12288
in my treemods I usually up these values twice or more as the draw ranges are now increased (via FLIGHTENGINE.INI DetailMeshSize= statements) to draw the TODs further away (thanks for your shaders too!) BUT when I lowered these values to zero I got no TOD objects, when it was small amounts only some of the meshes displayed on given corresponding tile. So I think the sim engine treats the TOD as more of objects data pool it uses to spawn the individual trees or buildings (or more accurately solidobjects and alphaobjects) on the given underlying tile, NOT as a single object- that also would make impossible to have the TODs populate slopes of any angle other than 0 degree of course. What is the biggest unknown for me, and your data seems to indicate is possible is if the TODs can have real 3D vertices orientation, meaning allowing more complex shapes than cubic/box ones (that can be done with 2.5D engine) As for "chance" value I do use it in some of my treemods for some buildings I for example don't want to spawn on every single tile in case that would create too obvious patterns. Say a barn near the field and such. That entry makes minimal usage though.
Sorry Mue if I didn't make myself clear, am bit sleepy today