Custom block models are incorrectly lit at low light levels

When using custom models for blocks (such as dripstone) the game will sometimes incorrectly render some faces of the model fully bright.

It happens when the block is on the edge between 1 and 0 block/sky light.

I don't think this should be classified as invalid because even tough it's only visible on non-vanilla block models this is a problem with the rendering engine itself rather than the texturepack.

Steps To Reproduce

1. Download the attached “enhanced dripstone” resourcepack

2. Download the (attached in a comment) “MC-238573.zip” reproduction world

3. The issue is visible upon enabling the resourcepack

Expected Behavior

These blocks wouldn't be fully lit at very low light levels

Observed Behavior

They are.