Inner faces of composters are all lit the same

Closely related to MCPE-170436.

The bug

The interior faces of composters are always lit the same as each other. This is inconsistent with other hollow blocks such as cauldrons, where the different faces are shaded differently depending on direction.

How to reproduce

1. Place a composter
2. Place a cauldron
3. Compare interiors

Expected results

The insides of composters would be at different brightness levels depending on their direction, much like the outside textures are.

Actual results

They appear as bright as each other.