When using bits from blocks the glow in the dark, but don't emit any light (ex. the screen blocks from Dave's Building Extended), the bits themselves do emit light when the light factor is set to 1.0. When the light factor is set to 0.0, the bits don't emit light, but also don't glow like the source block does.

MC version: 1.19.2
Forge version: 43.3.5
C&B version: 1.3.146

The source block - notice it glows, yet block light is 0

A bit from the green screen emitting a full light level

When light factor is 0.0, the bit no longer glows in the dark