I found this while updating a resourcepack for a map!
Then I digged into the minecraft.jar assets and found that the block model of granite still uses the old texture from name before the flattening

To be clear: the granite.json model refers to the granite_stone.png texture, which seems to be inconsistent regarding that the andesite.json model refers to the andesite.png texture, as every other stone model aswell!

So to fix this, the granite.json model should refer to the granite.png texture instead of granite_stone.png, which is how it currently is.