Found while testing the fix to MC-205840.

When shading blocks, smooth lighting often results in blocks underneath tinted glass, which should block 100% of light, being slightly lit if they have fully-lit neighbours. As tinted glass is meant to completely block light, light shouldn't visually show up here.

When smooth lighting is disabled, all faces occluded by tinted glass appear completely dark, which is what is also expected when smooth lighting is on.