You're both somewhat right and somewhat wrong.
They can be culled, just not by other ramps.
The reason is that the "coverage" part of the script determines whether it culls adjacent bricks or not.
The first attachment shows that it's side can be culled. I'm standing in a 8x Cube.
The second attachment shows that ramps do not cull other bricks, otherwise you'd be able to see through the side of this 2x2x3 brick, as shown in the third attachment.