There is no collision .dts for 6 sided bricks.
There could be, it depends what shape the brick is. If it were some sort of 6-faced cone like a pyramid with the top cut off, you'd need a collision dts.
Generally for rectangular/square bricks there is no need for a collision dts, its only when the shapes start to get non-regular (like the pine tree or the slopes) that it'd be much easier to just make a dts for the collision instead of trying to get close-fitting ones inside the blb.