Half-block dips are lit inconsistently depending on constituent blocks

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Central dip: 4 inner corner stairs

Edge dips: 2 regular stairs facing into each other

Corner dips: Slab blocks

The lighting seen across these different types of half-block descents is not consistent, when it obviously should be. Assuming the lighting applied to the slabs is the expected lighting effect.

To reproduce, recreate the structure and make sure Smooth Lighting is on.