Occasionally tallgrass generates underground, and with the absence of light sources it is very obvious that for some reason tallgrass emits a very slight amount of light. This happens despite the MER map being completely black in the emissive channel, and even happens when the MER is specified as [ 0, 0, 255 ] in the texture set file.

Steps to Reproduce: 

1. Join the attached world with Ray Tracing on while using the PBR resource pack linked below
2. Go to the coordinates 472 72 -45
3. Place tallgrass on the dirt in the middle of the concrete

Observed Results:

There is a very slight amount of green light emitted from the tallgrass, which is visible on the concrete nearby. This happens despite the tallgrass_mer.png file having no data whatsoever in the green channel.

Expected Results:

The tallgrass should not emit any sort of light due to it being specified to be non-emissive in the MER file.

Spore Blossoms:

To reproduce the issue for Spore Blossoms apply the attached PBR resources in a Ray Tracing resource pack and place a spore blossom in a place where the flower portion collides with the side of a block. It will start glowing despite being specified not to glow.

You can download the PBR resource pack I used to take these screenshots and demonstrate the issue here:
https://www.mediafire.com/file/r4iatv86doxtxfo/Defined_PBR_v1.0.4.mcpack/file