Tile Collision Question

I'm new to Torque, so forgive me if this is a dumb question. I'm using the PlatformStarterKit and TGB 1.7.4.

I'm having trouble getting wall collisions to work on TileLayer objects with the standard Platform behavior. I have three TileLayers forming a basin shape. The character can stand on top of any of them - he doesn't fall through from above - but he can walk through the sides. If I add in separate SceneObjects, on top of the TileLayers, and assign THEM the Platform behavior, it works the way I want it to.

But it seems silly that I would have to add separete SceneObjects for every TileLayer just to get wall collisions. After all, aren't TileLayers just children of SceneObjects anyway? Is there something different about the way TileLayers and SceneObjects handle collisions that would explain the inconsistency with which they react to being assigned the Platform behavior?

Thanks,
Nathan