[1.16] Texture metadata for textures in sublayers of generated item models does not work (?)

[ChloeDawn]

Mod version: MC1.16.1-1.1.0.1

In this case, I was attempting to add a glowing texture for the lava inside the lava bucket.
There are no messages or errors regarding this in the log.

lava_bucket.json

{
  "parent": "minecraft:item/generated",
  "textures": {
    "layer0": "minecraft:item/lava_bucket",
    "layer1": "coalescence:item/lava_bucket_0",
    "layer2": "coalescence:item/lava_bucket_1"
  }
}

lava_bucket_0.png.mcmeta

{
	"ctm": {
		"ctm_version": 1,
		"type": "normal",
		"layer": "CUTOUT",
		"extra": {
			"light": {
				"block": 8
			}
		}
	}
}

lava_bucket_1.png.mcmeta

{
	"ctm": {
		"ctm_version": 1,
		"type": "normal",
		"layer": "CUTOUT",
		"extra": {
			"light": {
				"block": 15
			}
		}
	}
}